array

☰std/array/any

Checks if the given array is present and it is not empty (contains at least one element).

Type signature

<T>(xs?: T[]) => boolean

Examples

any([]);
// ⇒ false

Try in REPL

any([1, 2, 3]);
// ⇒ true

Try in REPL

Questions

How to check if an array is empty?
How to check if an array is empty or null or undefined?
How to check if an array is empty or not?
How to check if an array is empty or doesn't exist?

TypeScript source • JavaScript source

☰std/array/are

Checks if the given arguments are all `Arrays`.

Type signature

<T>(...xs: T[]) => boolean

Examples

are([2, 3]);
// ⇒ true

Try in REPL

are([1, 2, 3], []);
// ⇒ true

Try in REPL

are([1, 2, 3], 8, [1, 3], "test");
// ⇒ false

Try in REPL

Questions

How to check if all the given values are arrays?

TypeScript source • JavaScript source

☰std/array/chunk

Splits the given array into an array of chunks of up to the given length.

Type signature

(count: number) => <T>(xs: T[]) => T[] | T[][]

Examples

chunk(2)(["a", "b", "c", "d"]);
// ⇒ [['a', 'b'], ['c', 'd']]

Try in REPL

chunk(3)(["a", "b", "c", "d"]);
// ⇒ [['a', 'b', 'c'], ['d']]

Try in REPL

Questions

How to split an array into chunks?
How to split an array into chunks of the same size?

TypeScript source • JavaScript source

☰std/array/difference

Computes a set difference between the two given arrays.

Type signature

<T>(xs: T[], ys: T[]) => T[]

Examples

difference(
  [1, 2, 3, 4, 5, 6],
  [2, 4],
);
// ⇒ [1, 3, 5, 6]

Try in REPL

Questions

How to find elements which are present in the first array and not in the second?

TypeScript source • JavaScript source

Type signature

<T>(xs?: T[], ys?: T[]) => boolean

Examples

differs([1, 2, 3], [1, 2]);
// ⇒ true

Try in REPL

differs([1, 2, 3], [1, 2, 3]);
// ⇒ false

Try in REPL

Questions

How to check if two arrays differ?
How to check if two arrays are not equal?
How to check if two arrays are equal or not?

TypeScript source • JavaScript source

☰std/array/duplicates

Lists all the duplicated values in the given array.

Type signature

<T>(xs: T[]) => T[]

Examples

duplicates([
  1, 2, 3, 4, 3, 4, 3, 6,
]);
// ⇒ [3, 4, 3]

Try in REPL

Questions

How to find duplicates in an array?

TypeScript source • JavaScript source

Type signature

unknown[]

Examples

empty;
// ⇒ []

Try in REPL

Questions

How to get an empty array?

TypeScript source • JavaScript source

☰std/array/exact

Takes exactly the given count of elements.

Type signature

(count: number) => <T>(xs: T[]) => T[]

Examples

exact(5)([1, 2, 3]);
// ⇒ [1, 2, 3, undefined, undefined]

Try in REPL

exact(2)([1, 2, 3]);
// ⇒ [1, 2]

Try in REPL

Questions

How to get exactly N elements out of an array?

TypeScript source • JavaScript source

Type signature

<T>(y: T) => (xs: T[]) => T[]

Examples

except(2)([1, 2, 3, 4, 5]);
// ⇒ [1, 3, 4, 5]

Try in REPL

except(2)([1, 2, 2, 4, 2]);
// ⇒ [1, 4]

Try in REPL

Questions

How to get all the values of an array except the given one?

TypeScript source • JavaScript source

☰std/array/filterInPlace

Filters the given array with the given predicate just like Array.filter but does it in-place thus mutates the original array.

Type signature

<T>(f: (value: T, index: number, context: T[]) => boolean) => (xs: T[]) => T[]

Examples

const xs = [1, 2, 3, 4, 5, 6, 7];
const odd = (x) => x % 2 === 1;

const ys = filterInPlace(odd)(xs);

ys === xs;
// ⇒ true
ys;
// ⇒ [1, 3, 5, 7]

Try in REPL

Questions

How to filter an array in place?

TypeScript source • JavaScript source

☰std/array/find

Finds an element by a predicate function within the given array, otherwise, it returns the given fallback value or undefined when fallback is not present.

Type signature

<T>(predicate: (value: T, index: number, context: T[]) => boolean, fallback?: T) => (xs: T[]) => T

Examples

find((x) => x > 2)([1, 2, 3, 5, 7]);
// ⇒ 3

Try in REPL

find((x) => x > 2)([
  1, 2, -3, -5, -7,
]);
// ⇒ undefined

Try in REPL

Questions

How to find an element of an array by a given predicate?

TypeScript source • JavaScript source

☰std/array/first

Returns the first element or undefined when there are no elements in the given array.

Type signature

<T>([x]: T[]) => T | undefined

Examples

first([1, 2, 3]);
// ⇒ 1

Try in REPL

first([]);
// ⇒ undefined

Try in REPL

Questions

How to get the first element of an array?

TypeScript source • JavaScript source

Type signature

<T, TResult>(f: (value: T, index: number, context: T[]) => TResult[]) => (xs: T[]) => TResult[]

Examples

flatMap((text) => [...text])([
  "test",
  "123",
]);
// ⇒ ["t", "e", "s", "t", "1", "2", "3"]

Try in REPL

Questions

How to flat map an array?
How to map and then flatten an array?

TypeScript source • JavaScript source

☰std/array/flatten

Flattens the nested arrays by a single level.

Type signature

<T>(xs: T[]) => T[]

Examples

flatten([1, [2, 3], 4, [5, 6]]);
// ⇒ [1, 2, 3, 4, 5, 6]

Try in REPL

flatten([
  1,
  [2, [3, 6]],
  4,
  [5, 6],
]);
// ⇒ [1, 2, [3, 6], 4, 5, 6]

Try in REPL

Questions

How to flatten an array?

TypeScript source • JavaScript source

☰std/array/insert

Inserts the given item to the array at a specific index.

Type signature

(index: number) => <T>(item: T) => ([...xs]: T[]) => T[]

Examples

insert(0)("d")(["a", "b", "c"]);
// ⇒ ['d', 'a', 'b', 'c']

Try in REPL

insert(1)("d")(["a", "b", "c"]);
// ⇒ ['a', 'd', 'b', 'c']

Try in REPL

Questions

How to insert an element to an array at a given position?

TypeScript source • JavaScript source

☰std/array/intersection

Finds common elements between both arrays.

Type signature

<T>(xs: T[], ys: T[]) => T[]

Examples

intersection(
  [1, 2, 3, 4, 5],
  [5, 5, 3, 2],
);
// ⇒ [2, 3, 5]

Try in REPL

Questions

How to find common elements present in both arrays?

TypeScript source • JavaScript source

☰std/array/is

Checks if the given argument is an array.

Type signature

(value?: unknown) => boolean

Examples

is([1, 2, 3]);
// ⇒ true

Try in REPL

is({ a: 5 });
// ⇒ false

Try in REPL

Questions

How to check if a value is an array?

TypeScript source • JavaScript source

☰std/array/last

Returns the last element or undefined when there are no elements in the given array.

Type signature

<T>(xs: T[]) => T | undefined

Examples

last([1, 2, 3]);
// ⇒ 3

Try in REPL

last([]);
// ⇒ undefined

Try in REPL

Questions

How to get the last element of an array?

TypeScript source • JavaScript source

☰std/array/length

Returns the number of elements in the given array.

Type signature

<T>(xs: T[]) => number

Examples

length([true, 1]);
// ⇒ 2

Try in REPL

length([1, 2, 3]);
// ⇒ 3

Try in REPL

length([]);
// ⇒ 0

Try in REPL

Questions

How to check an array's length?
How to compute an array's length?
How to check the size of an array?
How to check the number of elements in an array?

TypeScript source • JavaScript source

☰std/array/lengthDiffers

Checks if lengths of the given arrays differ.

Type signature

<T1, T2>(a: T1[], b: T2[]) => boolean

Examples

lengthDiffers([1, 2, 3], [1, 2]);
// ⇒ true

Try in REPL

lengthDiffers([6, 7], [1, 2]);
// ⇒ false

Try in REPL

Questions

How to check if array lengths differ?
How to check if the given arrays have different lengths?

TypeScript source • JavaScript source

☰std/array/map

Maps the given array with the given functions.

Type signature

<T>(...fs: ((x: T) => T)[]) => (xs: T[]) => T[]

Examples

map((x) => x * x)([1, 2, 3]);
// ⇒ [1, 4, 9]

Try in REPL

map(
  (x) => x * x,
  (x) => x + 1,
)([1, 2, 3]);
// ⇒ [2, 5, 10]

Try in REPL

Questions

How to map an array?

TypeScript source • JavaScript source

☰std/array/midpoint

Returns the middle element or the right one when the number of elements is even.

Type signature

<T>(xs: T[]) => T | undefined

Examples

midpoint([1, 2, 3, 4, 5]);
// ⇒ 3

Try in REPL

midpoint([1, 2, 3, 4]);
// ⇒ 3

Try in REPL

Questions

How to get the element in the middle of an array?
How to get the middle element of an array?

TypeScript source • JavaScript source

☰std/array/minMax

Computes minimum and maximum values of the given array in a single run.

Type signature

(xs: number[]) => number[]

Examples

minMax([
  10, 5, 3, -5, -4, 23, 32, 8, 1, 0,
]);
// ⇒ [-5, 32]

Try in REPL

minMax([1]);
// ⇒ [1, 1]

Try in REPL

minMax([]);
// ⇒ [undefined, undefined]

Try in REPL

Questions

How to find the minimum and maximum values of an array?
How to get the min/max element of an array?

TypeScript source • JavaScript source

☰std/array/multiple

Checks if the given array contains more than one element.

Type signature

<T>(xs: T[]) => boolean

Examples

multiple([1, 2, 3]);
// ⇒ true

Try in REPL

multiple([1, 2]);
// ⇒ true

Try in REPL

multiple([1]);
// ⇒ false

Try in REPL

multiple([]);
// ⇒ false

Try in REPL

Questions

How to check if an array contains multiple elements?
How to check whether multiple values exist within an array?

TypeScript source • JavaScript source

Type signature

<T>(xs?: T[]) => boolean

Examples

none([]);
// ⇒ true

Try in REPL

none([1, 2, 3]);
// ⇒ false

Try in REPL

Questions

How to check if an array is empty?

TypeScript source • JavaScript source

Partitions the given array to the ones that pass the given predicate function and the ones that do not. By [convention of the Haskell's Data.Either](http://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Either.html), values that pass the predicate are placed at the right.

Type signature

<T>(predicate: (x: T) => boolean) => (xs: T[]) => readonly [T[], T[]]

Examples

partition((x) => x % 2 === 1)([
  1, 2, 3, 4, 5,
]);
// ⇒ [[2, 4], [1, 3, 5]])

Try in REPL

Questions

How to partition an array based on a condition?
How to divide an array by a filter function?

TypeScript source • JavaScript source

☰std/array/pop

Returns the given array without the last element.

Type signature

<T>(xs: T[]) => T[]

Examples

pop([1, 2, 3, 4]); // ⇒ [1, 2, 3]

Try in REPL

pop([]); // ⇒ []

Try in REPL

Questions

How to get an array without the last element?
How to remove the last element from an array?

TypeScript source • JavaScript source

☰std/array/range

Generates an array of numbers from 0 to n - 1.

Type signature

(n: number) => number[]

Examples

range(3);
// ⇒ [0, 1, 2]

Try in REPL

Questions

How to create an array of all integers from 0 to N exclusive?

TypeScript source • JavaScript source

☰std/array/removeAt

Removes an element at the given index from the given array.

Type signature

(index: number) => <T>(xs: T[]) => T[]

Examples

removeAt(3)([1, 2, 3, 4, 5, 6]);
// ⇒ [1, 2, 3, 5, 6]

Try in REPL

Questions

How to remove an item from an array at a particular index?

TypeScript source • JavaScript source

☰std/array/repeat

Repeats the given element by the given count of times.

Type signature

(count: number) => <T>(value: T) => T[]

Examples

repeat(3)("test");
// ⇒ ["test", "test", "test"]

Try in REPL

Questions

How to repeat a value N times?

TypeScript source • JavaScript source

☰std/array/reverse

Reverses the given array without mutating it (in contrast to Array.reverse).

Type signature

<T>(xs: T[]) => T[]

Examples

reverse([1, 2, 3, 4, 5]);
// ⇒ [5, 4, 3, 2, 1]

Try in REPL

Questions

How to reverse an array without mutating it?

TypeScript source • JavaScript source

☰std/array/reverseIf

Reverses the given array when enabled.

Type signature

(enabled: boolean) => <T>(xs: T[]) => T[]

Examples

reverseIf(true)([1, 2, 3, 4, 5]);
// ⇒ [5, 4, 3, 2, 1]

Try in REPL

reverseIf(false)([1, 2, 3, 4, 5]);
// ⇒ [1, 2, 3, 4, 5]

Try in REPL

Questions

How to reverse an array without mutating it only when a condition is satisfied?

TypeScript source • JavaScript source

☰std/array/second

Returns the second element or undefined when there are less than two elements in the given array.

Type signature

<T>(xs: T[]) => T | undefined

Examples

second([1, 2, 3, 4, 5]);
// ⇒ 2

Try in REPL

second([1]);
// ⇒ undefined

Try in REPL

second([]);
// ⇒ undefined

Try in REPL

Questions

How to get the second element of an array?

TypeScript source • JavaScript source

☰std/array/secondToLast

Returns the second to last element or undefined when there are less than two elements in the given array.

Type signature

<T>(xs: T[]) => T | undefined

Examples

secondToLast([1, 2, 3, 4, 5]);
// ⇒ 4

Try in REPL

secondToLast([1]);
// ⇒ undefined

Try in REPL

secondToLast([]);
// ⇒ undefined

Try in REPL

Questions

How to get the second to last element of an array?

TypeScript source • JavaScript source

☰std/array/shift

Shifts the given array to the left and circulates the elements back by modulo of the array's length.

Type signature

(count: number) => <T>(xs: T[]) => T[]

Examples

shift(1)([1, 2, 3, 4, 5]);
// ⇒ [2, 3, 4, 5, 1]

Try in REPL

shift(2)([1, 2, 3, 4, 5]);
// ⇒ [3, 4, 5, 1, 2]

Try in REPL

shift(3)([1, 2, 3, 4, 5]);
// ⇒ [4, 5, 1, 2, 3]

Try in REPL

Questions

How to shift an array?

TypeScript source • JavaScript source

☰std/array/shuffle

Shuffles the given array in random order with Math.random as the default.

Type signature

<T>(xs: T[], random?: () => number) => T[]

Examples

let i = 0;

const random = () =>
  [
    0.013606630487694282,
    0.21052486239086554,
    0.28299838254636556,
    0.696161009199874,
    0.32165320593537117,
  ][i++];

shuffle([1, 2, 3, 4, 5], random); // => [3, 5, 4, 2, 1]

Try in REPL

Questions

How to shuffle an array?

TypeScript source • JavaScript source

☰std/array/shuffleInPlace

Shuffles the given array in-place in random order with Math.random as the default.

Type signature

<T>(xs: T[], random?: () => number) => T[]

Examples

let i = 0;

const random = () =>
  [
    0.013606630487694282,
    0.21052486239086554,
    0.28299838254636556,
    0.696161009199874,
    0.32165320593537117,
  ][i++];

shuffleInPlace(
  [1, 2, 3, 4, 5],
  random,
); // => [3, 5, 4, 2, 1]

Try in REPL

Questions

How to shuffle an array in place?

TypeScript source • JavaScript source

☰std/array/single

Checks if the given array contains exactly one element.

Type signature

<T>(xs: T[]) => boolean

Examples

single([1]);
// ⇒ true

Try in REPL

single([1, 2, 3]);
// ⇒ false

Try in REPL

single([]);
// ⇒ false

Try in REPL

Questions

How to check if an array contains only one element?

TypeScript source • JavaScript source

☰std/array/skip

Skips the given count of elements from the given array.

Type signature

(count: number) => <T>(xs: T[]) => T[]

Examples

skip(2)([1, 2, 3, 4, 5]);
// ⇒ [3, 4, 5]

Try in REPL

Questions

How to skip the first few elements of an array?

TypeScript source • JavaScript source

☰std/array/slidingWindow

Returns a new array composed of tuples of the given sliding window length of consecutive elements.

Type signature

(count: number) => <T>(xs: T[]) => T[][]

Examples

slidingWindow(2)([1, 2, 3, 4]);
// ⇒ [[1, 2], [2, 3], [3, 4]]

Try in REPL

slidingWindow(3)([1, 2, 3, 4, 5]);
// ⇒ [[1, 2, 3], [2, 3, 4], [3, 4, 5]]

Try in REPL

slidingWindow(1)([
  1, 2, 3, 4, 5, 6,
]);
// ⇒ [[1], [2], [3], [4], [5], [6]]

Try in REPL

Questions

How to iterate an array pairwise?

TypeScript source • JavaScript source

☰std/array/sort

Sorts the given array without mutating it.

Type signature

<T>(f?: (a: T, b: T) => number) => (xs: T[]) => T[]

Examples

sort((a, b) => a - b)([
  13, 79, 20, 69, 44, 67, 18, 95,
  26, 55,
]);
// ⇒ [13, 18, 20, 26, 44, 55, 67, 69, 79, 95]

Try in REPL

Questions

How to sort an array without mutating it?

TypeScript source • JavaScript source

☰std/array/sum

Sums the given array of numbers.

Type signature

(xs: number[]) => number

Examples

sum([1, 2, 3, 4, 5]);
// ⇒ 15

Try in REPL

Questions

How to sum elements of an array?

TypeScript source • JavaScript source

☰std/array/take

Takes up to a given count of elements.

Type signature

(count: number) => <T>(xs: T[]) => T[]

Examples

take(2)([1, 2, 3, 4, 5]);
// ⇒ [1, 2]

Try in REPL

take(10)([1, 2, 3, 4, 5]);
// ⇒ [1, 2, 3, 4, 5]

Try in REPL

Questions

How to get the first N number of elements from an array?

TypeScript source • JavaScript source

☰std/array/unique

Returns unique elements of the given array.

Type signature

<T>(xs: T[]) => T[]

Examples

unique([1, 2, 3, 4, 3, 4, 3, 6]);
// ⇒ [1, 2, 3, 4, 6]

Try in REPL

Questions

How to find all unique values in an array?

TypeScript source • JavaScript source

☰std/array/uniqueBy

Filters out duplicated values based on the result of the given key selector.

Type signature

<T, TResult>(f: (x: T) => TResult) => (xs: T[]) => T[]

Examples

uniqueBy(({ id }) => id)([
  { id: 1, value: "a" },
  { id: 2, value: "b" },
  { id: 1, value: "c" },
]);
// ⇒ [{ id: 1, value: 'c' }, { id: 2, value: 'b' }]

Try in REPL

Questions

How to find all unique values in an array by some predicate?

TypeScript source • JavaScript source

☰std/array/zip

Zips the given arrays together into pairs.

Type signature

(xs: unknown[], ys: unknown[]) => [unknown, unknown][]

Examples

zip([1, 2, 3], [4, 5, 6]);
// ⇒ [[1, 4],[2, 5],[3, 6]]

Try in REPL

Questions

How to zip two arrays?

TypeScript source • JavaScript source

☰std/array/zipN

Zips the given arrays together into pairs.

Type signature

<T>(...xs: T[][]) => T[][]

Examples

zipN([1, 2, 3], [4, 5, 6]);
// ⇒ [[1, 4], [2, 5], [3, 6]]

Try in REPL

zipN(
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 9],
);
// ⇒ [[1, 4, 7], [2, 5, 8], [3, 6, 9]]

Try in REPL

zipN([1, 2], [4, 5, 6], [7, 8, 9]);
// ⇒ [[1, 4, 7],[2, 5, 8]]

Try in REPL

Questions

How to zip multiple arrays?

TypeScript source • JavaScript source

☰std/array/zipWith

Zips the given arrays together with the given function.

Type signature

<T1, T2>(f?: (x: T1, y: T2) => [T1, T2]) => (xs: T1[], ys: T2[]) => [T1, T2][]

Examples

zipWith((x, y) => x * x + y)(
  [1, 2, 3],
  [4, 5, 6],
);
// ⇒ [5, 9, 15]

Try in REPL

Questions

How to zip two arrays with a given function?

TypeScript source • JavaScript source

async

☰std/async/debounce

Makes the function run after the given period of not being called. Useful to delay input submission for auto-complete etc.

Type signature

(f: F, wait: number) => (...args: unknown[]) => void

Examples

const f = () => console.log("Test");

const debounced = debounce(f, 2000);

debounced();
setTimeout(debounced, 1000);
setTimeout(debounced, 3000);

Try in REPL

Questions

How to make function fire after some time not being called?
How to debounce input events?
How to debounce a function?

TypeScript source • JavaScript source

☰std/async/delay

When awaited, delays the execution by the given number of milliseconds.

Type signature

(duration: number) => Promise<unknown>

Examples

delay(2000)(() =>
  console.log("Test"),
);

Try in REPL

Questions

How to delay a function?
What is the JavaScript version of sleep()?

TypeScript source • JavaScript source

☰std/async/sequence

Runs the given tasks in a sequence.

Type signature

<T>(tasks: Task<T>[]) => Promise<Awaited<T>[]>

Examples

const f = () =>
  new Promise((resolve) =>
    setTimeout(resolve, 1000),
  );
const g = () =>
  new Promise((resolve) =>
    setTimeout(resolve, 2000),
  );

sequence([f, g]).then(() =>
  console.log("Done"),
);

Try in REPL

Questions

How to run async tasks sequentially?

TypeScript source • JavaScript source

date

☰std/date/clamp

Clamps the given date to the given date range.

Type signature

(min: Date, max: Date) => (date: Date) => Date

Examples

const date = new Date(
  "2019-06-15T13:54:33.232Z",
);
const min = new Date(
  "2019-02-23T13:54:33.232Z",
);
const max = new Date(
  "2019-03-13T13:54:33.232Z",
);

clamp(min, max)(date);
// => new Date("2019-03-13T13:54:33.232Z")

Try in REPL

Questions

How to clamp a date to the desired date range?
How to enforce a date to be in a given date range?

TypeScript source • JavaScript source

☰std/date/clone

Clones the given Date object.

Type signature

(date: Date) => Date

Examples

const date = new new Date(
  "2019-04-24T13:54:33.232Z",
)();
const cloned = clone(date);

cloned !== date &&
  cloned.valueOf() ===
    date.valueOf();
// ⇒ true

Try in REPL

Questions

How to clone a Date object?

TypeScript source • JavaScript source

☰std/date/dateDiff

Computes a signed difference between two Date objects as milliseconds.

Type signature

(a: Date, b: Date) => number

Examples

dateDiff(
  new Date(
    "2017-01-01T13:00:00.000Z",
  ),
  new Date(
    "2017-01-01T12:00:00.000Z",
  ),
);
// ⇒ 3600000

Try in REPL

Questions

How to compute Date difference?

TypeScript source • JavaScript source

☰std/date/dateInRange

Checks if the given date is between the given date range (inclusive).

Type signature

(from: Date, to: Date) => (date: Date) => boolean

Examples

dateInRange(
  new Date(
    "2018-06-10T12:00:00.000Z",
  ),
  new Date(
    "2018-06-20T12:00:00.000Z",
  ),
)(
  new Date(
    "2018-06-15T12:00:00.000Z",
  ),
);
// ⇒ true

Try in REPL

Questions

How to check if a date is within a given date range?

TypeScript source • JavaScript source

☰std/date/dayRange

Returns a local day range at a particular Date.

Type signature

(date: Date) => Date[]

Examples

const date = new Date(
  "2018-12-31T13:54:33.232Z",
);

dayRange(date);
// ⇒ [startOfDay(date), endOfDay(date)]

Try in REPL

Questions

How to find a date range of a given day?

TypeScript source • JavaScript source

☰std/date/daysInMonths

Returns an array of days in a particular months. Number of days in February varies if it is a leap year or not.

Type signature

(leapYear: boolean) => [number, number, number, number, number, number, number, number, number, number, number, number]

Examples

daysInMonths(false);
// ⇒ [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

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daysInMonths(true);
// ⇒ [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

Try in REPL

Questions

How to find out how many days are in a particular month?
How to find out how many days there are in a leap year?

TypeScript source • JavaScript source

☰std/date/daysInYear

Calculates the number of days in a particular year. Varies by the leap year.

Type signature

(year: number) => 366 | 365

Examples

daysInYear(2019);
// ⇒ 365

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daysInYear(2020);
// ⇒ 366

Try in REPL

Questions

How many days are in a particular year?
How many days are in a leap year?
How many days are in a common year?

TypeScript source • JavaScript source

☰std/date/displayTime

Displays padded time string.

Type signature

(source: [number, number, number], showSeconds: boolean) => string

Examples

displayTime([5, 12, 16], false);
// ⇒ 05:12

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displayTime([5, 12, 16], true);
// ⇒ 05:12:16

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Questions

How to display padded time?

TypeScript source • JavaScript source

☰std/date/endOfDay

Returns a local Date of an end of the day at a particular Date.

Type signature

(date: Date) => Date

Examples

endOfDay(
  new Date(
    "2018-12-31T13:54:33.232Z",
  ),
);
// ⇒ new Date(new Date("2019-01-01T00:00:00.000Z").valueOf() + new Date("2018-12-31T13:54:33.232Z").getTimezoneOffset() * 60 * 1000)

Try in REPL

Questions

How to find a date of an end of a given day?

TypeScript source • JavaScript source

☰std/date/formatDate

Formats a given date as a simple YYYY-MM-DD string.

Type signature

(date: Date) => string

Examples

formatDate(
  new Date("2019-02-24T01:12:34"),
);
// ⇒ "2019-02-24"

Try in REPL

Questions

How to render a date in a YYYY-MM-DD format?

TypeScript source • JavaScript source

☰std/date/formatDateTime

Formats a given date as a simple YYYY-MM-DD HH:MM(:SS) string.

Type signature

(sourceDate: Date, showSeconds?: boolean) => string

Examples

formatDateTime(
  new Date("2019-02-24T01:12:34"),
);
// ⇒ "2019-02-24 01:12"

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formatDateTime(
  new Date("2019-02-24T01:12:34"),
  true,
);
// ⇒ "2019-02-24 01:12:34"

Try in REPL

Questions

How to render a date in a YYYY-MM-DD HH:MM format?
How to render a date in a YYYY-MM-DD HH:MM:SS format?

TypeScript source • JavaScript source

☰std/date/formatDuration

Formats a duration in milliseconds to a padded time string.

Type signature

(duration: number, showSeconds?: boolean) => string

Examples

formatDuration(26100000);
// ⇒ 07:15

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formatDuration(26136000, true);
// ⇒ 07:15:36

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Questions

How to render a formatted duration?

TypeScript source • JavaScript source

☰std/date/formatTime

Formats a given date as a simple HH:MM(:SS) string.

Type signature

(date: Date, showSeconds?: boolean) => string

Examples

formatTime(
  new Date("2019-02-24T01:12:34"),
);
// ⇒ "01:12"

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formatTime(
  new Date("2019-02-24T01:12:34"),
  true,
);
// ⇒ "01:12:34"

Try in REPL

Questions

How to render a date in a HH:MM format?
How to render a date in a HH:MM:SS format?

TypeScript source • JavaScript source

☰std/date/fromDays

Converts the given day count to milliseconds.

Type signature

(days: number) => number

Examples

fromDays(1);
// ⇒ 86400000

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Questions

How to find how many milliseconds are in a given number of days?

TypeScript source • JavaScript source

☰std/date/fromHours

Converts the given hour count to milliseconds.

Type signature

(hours: number) => number

Examples

fromHours(1);
// ⇒ 3600000

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Questions

How to find how many milliseconds are in a given number of hours?

TypeScript source • JavaScript source

☰std/date/fromMinutes

Converts the given minute count to milliseconds.

Type signature

(minutes: number) => number

Examples

fromMinutes(1);
// ⇒ 60000

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Questions

How to find how many milliseconds are in a given number of minutes?

TypeScript source • JavaScript source

☰std/date/fromSeconds

Converts the given second count to milliseconds.

Type signature

(seconds: number) => number

Examples

fromSeconds(1);
// ⇒ 1000

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Questions

How to find how many milliseconds are in a given number of seconds?

TypeScript source • JavaScript source

☰std/date/joinDateTime

Joins a date-time pair into a date-time string.

Type signature

(date: string, time: string) => string

Examples

joinDateTime(
  "2019-01-15",
  "13:54:33.232Z",
);
// ⇒ "2019-01-15T13:54:33.232Z"

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Questions

How to join date and time to get ISO-compliant date-time string?

TypeScript source • JavaScript source

☰std/date/leapYear

Detects if a given year is a leap year.

Type signature

(year: number) => boolean

Examples

leapYear(2020);
// ⇒ true

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leapYear(2019);
// ⇒ false

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Questions

How to find if the given year is a leap year?

TypeScript source • JavaScript source

☰std/date/parseHourMinutePair

Parses HH:MM string into hours and minutes.

Type signature

(text?: string) => [number, number]

Examples

parseHourMinutePair("12:34");
// ⇒ [12, 34]

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Questions

How to parse time string into hours and minutes?

TypeScript source • JavaScript source

☰std/date/splitDateTime

Splits a date-time string into a date-time pair.

Type signature

(dateTimeString: string) => [string, string]

Examples

splitDateTime(
  "2019-01-15T13:54:33.232Z",
);
// ⇒ ["2019-01-15", "13:54:33.232Z"]

Try in REPL

Questions

How to split ISO-compliant date-time string into a date and time pair?

TypeScript source • JavaScript source

☰std/date/startOfDay

Returns a local Date of a start of the day at a particular Date.

Type signature

(date: Date) => Date

Examples

endOfDay(
  new Date(
    "2019-01-01T13:54:33.232Z",
  ),
);
// ⇒ new Date(new Date("2019-01-01T00:00:00.000Z").valueOf() + new Date("2019-01-01T13:54:33.232Z").getTimezoneOffset() * 60 * 1000)

Try in REPL

Questions

How to find a date of the start of a given day?

TypeScript source • JavaScript source

☰std/date/subtractDays

Subtracts the given number of days from the given Date object.

Type signature

(sourceDate: Date, numberOfDays: number) => Date

Examples

subtractDays(
  new Date(
    "2019-01-15T13:54:33.232Z",
  ),
  1,
);
// ⇒ new Date("2019-01-14T13:54:33.232Z")

Try in REPL

Questions

How to subtract days from a given date?

TypeScript source • JavaScript source

☰std/date/toDate

Extracts padded YYYY-MM-DD date string out of the given date object.

Type signature

(date: Date) => string

Examples

toDate(
  new Date(
    "2019-01-15T12:00:00.000Z",
  ),
);
// ⇒ "2019-01-15"

Try in REPL

Questions

How to get only the date from a Date object?

TypeScript source • JavaScript source

☰std/date/toDates

Converts the given array of values into Dates using the Date constructor.

Type signature

(xs: (string | number | Date)[]) => Date[]

Examples

toDates([
  "2019-01-15T13:54:33.232Z",
  new Date(
    "2019-01-15T13:54:33.232Z",
  ).valueOf(),
  new Date(
    "2019-01-15T13:54:33.232Z",
  ),
]);
// ⇒ [new Date("2019-01-15T13:54:33.232Z"), new Date("2019-01-15T13:54:33.232Z"), new Date("2019-01-15T13:54:33.232Z")]

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Questions

How to convert an array of string and timestamps into an array of Date objects?

TypeScript source • JavaScript source

☰std/date/toDays

Converts milliseconds into days.

Type signature

(milliseconds: number) => number

Examples

toDays(86400000);
// ⇒ 1

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Questions

How to convert milliseconds into days?

TypeScript source • JavaScript source

☰std/date/toHours

Converts milliseconds into hours.

Type signature

(milliseconds: number) => number

Examples

toHours(3600000);
// ⇒ 1

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Questions

How to convert milliseconds into hours?

TypeScript source • JavaScript source

☰std/date/toISO

Returns an ISO-compliant date-time string.

Type signature

(x: Date) => string

Examples

toISO(
  new Date(
    "2019-04-24T13:54:33.232Z",
  ),
);
// ⇒ "2019-04-24T13:54:33.232Z"

Try in REPL

Questions

How to convert Date object to ISO-compliant date string?

TypeScript source • JavaScript source

☰std/date/toMinutes

Converts milliseconds into minutes.

Type signature

(milliseconds: number) => number

Examples

toMinutes(60000);
// ⇒ 1

Try in REPL

Questions

How to convert milliseconds into minutes?

TypeScript source • JavaScript source

☰std/date/toSeconds

Converts milliseconds into seconds.

Type signature

(milliseconds: number) => number

Examples

toSeconds(1000);
// ⇒ 1

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Questions

How to convert milliseconds into seconds?

TypeScript source • JavaScript source

☰std/date/valid

Checks if the given date is present and it is valid.

Type signature

(date?: unknown) => boolean

Examples

valid(
  new Date(
    "2020-01-31T09:52:31.618Z",
  ),
);
// ⇒ true

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valid(
  new Date("2020-01-42:52:31.618Z"),
);
// ⇒ false

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valid(new Date("test"));
// ⇒ false

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valid(undefined);
// ⇒ false

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Questions

How to check if a Date is valid or not?

TypeScript source • JavaScript source

debug

☰std/debug/assert

Asserts given conditions.

Type signature

(condition: boolean, callbackOrMessage?: (() => void) | string) => void;
export declare const throws: (f: () => void) => unknown | undefined;
export declare const assertNumber: (x?: unknown) => void;
export declare const assertInteger: (x?: unknown) => void;
export declare const assertByte: (x?: unknown) => void;
export declare const assertNormal: (x?: unknown) => void;
export declare const assertString: (x?: unknown, message?: string) => void;
export declare const assertIsDefined: (x?: unknown, message?: string) => void;
export default assert

Examples

assert(true === false);
// ⇒ TypeError("Assertion failed!")

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Questions

How to assert a condition?
How to throw when a condition is not satisfied?

TypeScript source • JavaScript source

☰std/debug/diff

Computes a deep difference between the two values (primitives, objects, arrays, etc.).

Type signature

(obj1?: unknown, obj2?: unknown) => DiffResult;
export default diff

Examples

diff({ a: 1 }, { a: 2 });
// ⇒ { a: { data: [1, 2], type: '~' }}

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Questions

How to compute a diff?
How to compute a deep diff?
How to compute a diff between two objects?
How to compute a diff between two arrays?

TypeScript source • JavaScript source

base64url

☰std/encoding/base64url/decode

Decodes the given Base64URL back into a string.

Type signature

(text: string, context?: DecodeContext) => string

Examples

decode("PDw_Pz8-Pg");
// ⇒ "<<???>>"

Try in REPL

Questions

How to decode Base64URL?

TypeScript source • JavaScript source

☰std/encoding/base64url/decodeBytes

Decodes the given Base64URL back into a byte array.

Type signature

(text: string, context?: DecodeContext) => number[]

Examples

decodeBytes("w4Jnw6vCp20-bBsQfA");
// ⇒ [0xc2, 0x67, 0xeb, 0xa7, 0x6d, 0x3e, 0x6c, 0x1b, 0x10, 0x7c]

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Questions

How to decode Base64URL into a byte array?

TypeScript source • JavaScript source

☰std/encoding/base64url/encode

Encodes the given string into Base64URL.

Type signature

(text: string, context?: EncodeContext) => string

Examples

encode("<<???>>");
// ⇒ "PDw_Pz8-Pg"

Try in REPL

Questions

How to encode a string as Base64URL?

TypeScript source • JavaScript source

☰std/encoding/base64url/encodeBytes

Encodes the given bytes into Base64URL.

Type signature

(bytes: number[], context?: EncodeContext) => string

Examples

encodeBytes([
  0xc2, 0x67, 0xeb, 0xa7, 0x6d,
  0x3e, 0x6c, 0x1b, 0x10, 0x7c,
]);
// ⇒ "w4Jnw6vCp20-bBsQfA"

Try in REPL

Questions

How to encode bytes as Base64URL?

TypeScript source • JavaScript source

☰std/encoding/base64url/fromBase64

Converts Base64 string into Base64URL one.

Type signature

(base64: string) => string

Examples

fromBase64("PDw/Pz8+Pg==");
// ⇒ "PDw_Pz8-Pg"

Try in REPL

Questions

How to convert Base64 to Base64URL?

TypeScript source • JavaScript source

☰std/encoding/base64url/toBase64

Converts Base64URL string into Base64 one.

Type signature

(base64Url: string) => string

Examples

toBase64("PDw_Pz8-Pg");
// ⇒ "PDw/Pz8+Pg=="

Try in REPL

Questions

How to convert Base64URL to Base64?

TypeScript source • JavaScript source

byteString

☰std/encoding/byteString/from

Converts a string to a byte array.

Type signature

(byteString: string) => number[]

Examples

from("PQR");
// ⇒ [80, 81, 82]

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Questions

How to convert a string into a byte array?

TypeScript source • JavaScript source

☰std/encoding/byteString/to

Coverts a byte array into a string.

Type signature

(bytes: number[]) => string

Examples

to([0x50, 0x51, 0x52]);
// ⇒ "PQR"

Try in REPL

Questions

How to convert a byte array to string?

TypeScript source • JavaScript source

file

☰std/file/validName

Checks if the given string is a valid Windows file name.

Type signature

(name: string) => boolean

Examples

validName("my:file.png");
// ⇒ false

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validName("file.txt");
// ⇒ true

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validName("../file.txt");
// ⇒ false

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validName("COM1");
// ⇒ false

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Questions

How to find valid Windows file name?
How to check if a given string is a legal/valid file name under Windows?

TypeScript source • JavaScript source

function

☰std/function/compose

Composes multiple functions into a higher-order one. Goes right to left.

Type signature

<T, TResult>(...fs: ((x: T) => T)[]) => (x: T) => T

Examples

compose(
  (x) => x * x,
  (x) => x + 1,
)(3);
// ⇒ 16

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Questions

How to compose functions?

TypeScript source • JavaScript source

☰std/function/constant

Returns the given constant no matter the input.

Type signature

<T>(x: T) => () => T

Examples

constant(3)("anything");
// ⇒ 3

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Questions

How to create a function that always returns the same value despite given arguments?

TypeScript source • JavaScript source

☰std/function/identity

Always return the given value.

Type signature

<T>(x: T) => T

Examples

identity(5);
// ⇒ 5

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identity("test");
// ⇒ "test"

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Questions

How to use the identity function?
Where and why is identity function useful?

TypeScript source • JavaScript source

☰std/function/memoize

Memoizes the function result so it is not computed for the same parameters. Uses deep equality.

Type signature

<TResult>(f: (...xs: unknown[]) => TResult) => (...args: unknown[]) => TResult

Examples

const f = (x) => {
  console.log(x);
  return x + 1;
};

const memoized = memoize(f);

memoized(5);
memoized(5);
memoized(5);
memoized(3);

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Questions

How to memoize a function?

TypeScript source • JavaScript source

☰std/function/memoizeShallow

Memoizes the function result so it is not computed for the same parameters. Uses shallow equality.

Type signature

<TResult>(f: (...xs: unknown[]) => TResult) => (...args: unknown[]) => TResult

Examples

const f = ({ x }) => {
  console.log(x);
  return x + 1;
};

const memoized = memoizeShallow(f);

memoized({ x: 5 });
memoized({ x: 5 });
memoized({ x: 5 });
memoized({ x: 3 });

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Questions

How to memoize a function with shallow equality?

TypeScript source • JavaScript source

☰std/function/memoizeWith

Memoizes the function result so it is not computed for the same parameters. Uses the given equality function.

Type signature

<T>(equals: (x: T[], y: T[]) => boolean) => <TResult>(f: (...xs: T[]) => TResult) => (...args: T[]) => TResult

Examples

const f = ({ x }) => {
  console.log(x);
  return x + 1;
};

const memoized = memoizeWith(
  (a, b) => a.x === b.x,
)(f);

memoized({ x: 5 });
memoized({ x: 5 });
memoized({ x: 5 });
memoized({ x: 3 });

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Questions

How to memoize a function with a custom equality function?

TypeScript source • JavaScript source

☰std/function/noOp

It does exactly nothing.

Type signature

() => void

Examples

noOp("anything");
// ⇒ undefined

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Questions

How to create a function that does nothing?

TypeScript source • JavaScript source

☰std/function/not

Inverts the given function result.

Type signature

(f: (...xs: unknown[]) => unknown) => (...args: unknown[]) => boolean

Examples

not(x > 10)(15);
// ⇒ true

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Questions

How to invert a boolean function?

TypeScript source • JavaScript source

☰std/function/pipe

Pipes an input through given functions.

Type signature

<T>(...fs: ((x: T) => T)[]) => (x: T) => T

Examples

pipe(
  (x) => x * x,
  (x) => x + 1,
)(3);
// ⇒ 10

Try in REPL

Questions

How to pipe an argument through a function?

TypeScript source • JavaScript source

☰std/function/when

Runs the given function only when the condition is met.

Type signature

(predicate: (...xs: unknown[]) => boolean) => (action: (...xs: unknown[]) => unknown) => (...args: unknown[]) => unknown

Examples

when((x) => x > 0)((x) =>
  console.log(x),
)(5);
when((x) => x > 0)((x) =>
  console.log(x),
)(-3);

Try in REPL

Questions

How to run a function only when a condition is satisfied?

TypeScript source • JavaScript source

☰std/function/whenTrue

Runs the given function only when the condition is exactly true.

Type signature

(action: (...xs: unknown[]) => unknown) => (...args: unknown[]) => unknown

Examples

whenTrue((x) => console.log(x))(
  false,
);
when((x) => x > 0)((x) =>
  console.log(x),
)(true);

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Questions

How to run a function only if its argument is true?
How to execute function only if a variable is true?

TypeScript source • JavaScript source

is

☰std/is/array

Checks if the given argument is an array.

Type signature

(x?: unknown) => boolean

Examples

array([1, 2, 3]);
// ⇒ true

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array({ a: 1 });
// ⇒ false

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Questions

How to check if a given value is an array?

TypeScript source • JavaScript source

☰std/is/boolean

Checks if the given value is a boolean.

Type signature

(x?: unknown) => x is boolean

Examples

boolean(false); // ⇒ true

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boolean(1); // ⇒ false

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Questions

How to check if a given value is a boolean?

TypeScript source • JavaScript source

☰std/is/byte

Checks if the given value is a byte.

Type signature

(x?: unknown) => boolean

Examples

byte(128);
// ⇒ true

Try in REPL

byte(325);
// ⇒ false

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byte(65.5);
// ⇒ false

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Questions

How to check if a given value is a byte?
How to check if a given number is a byte?

TypeScript source • JavaScript source

☰std/is/date

Checks if the given value is a Date object.

Type signature

(x?: unknown) => boolean

Examples

date(new Date());
// ⇒ true

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date(123);
// ⇒ false

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Questions

How to check if a given value is a Date object?

TypeScript source • JavaScript source

☰std/is/defined

Checks if the given value is defined.

Type signature

(x?: unknown) => boolean

Examples

defined(undefined);
// ⇒ false

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defined(null);
// ⇒ true

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defined(0);
// ⇒ true

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defined({ a: 1 });
// ⇒ true

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Questions

How to check if a given value is defined?
How to check if a given value is not undefined?

TypeScript source • JavaScript source

☰std/is/function

Checks if the given value is a function.

Type signature

(x?: unknown) => x is Function

Examples

_function((x) => x + 5);
// ⇒ true

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Questions

How to check if a given value is a function?

TypeScript source • JavaScript source

☰std/is/integer

Checks if the given value is an integer.

Type signature

(x?: unknown) => boolean

Examples

integer(5);
// ⇒ true

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integer(32.5);
// ⇒ false

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Questions

How to check if a given value is an integer?
How to check if a given number is an integer?

TypeScript source • JavaScript source

☰std/is/nonNullable

Checks and asserts the given value is not null or undefined.

Type signature

<T>(val: T) => val is NonNullable<T>

Examples

nonNullable(null);
// ⇒ false

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nonNullable(undefined);
// ⇒ false

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nonNullable(false);
// ⇒ true

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nonNullable({ a: 1 });
// ⇒ true

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Questions

How to check if a given value is non-nullable?
How to check if a given value is not null?
How to check if a given value is not undefined?

TypeScript source • JavaScript source

☰std/is/normal

Checks if the given value is a number in a normal range [0, 1].

Type signature

(x?: unknown) => boolean

Examples

normal(0.75);
// ⇒ true

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normal(-1);
// ⇒ false

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normal(2.5);
// ⇒ false

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Questions

How to check if a given value is in 0 to 1 inclusive range?

TypeScript source • JavaScript source

☰std/is/number

Checks if the given value is a number.

Type signature

(x?: unknown) => boolean

Examples

number(0 / 0);
// ⇒ false

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number(15.6);
// ⇒ true

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Questions

How to check if a given value is a valid number?
How to check if a given value is not NaN?
How to check if a given value is finite?

TypeScript source • JavaScript source

☰std/is/object

Checks if the given value is an object.

Type signature

(x?: unknown) => boolean

Examples

object({ a: 1, b: 2 });
// ⇒ true

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object([1, 2, 3]);
// ⇒ false

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Questions

How to check if a given value is an object?

TypeScript source • JavaScript source

☰std/is/string

Checks if the given value is a string.

Type signature

(x?: unknown) => x is string

Examples

string("Test");
// ⇒ true

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string(["T", "e", "s", "t"]);
// ⇒ false

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Questions

How to check if a given value is a string?

TypeScript source • JavaScript source

math

☰std/math/add

Adds two values.

Type signature

(a: number, b: number) => number

Examples

add(3, 5);
// ⇒ 8

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Questions

How to add two values?

TypeScript source • JavaScript source

☰std/math/average

Calculates the average of the given array of numbers.

Type signature

(xs?: number[]) => number

Examples

average([2, 4, 15]);
// ⇒ 7

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Questions

How to compute the average of an array?

TypeScript source • JavaScript source

☰std/math/ceilToNearestPowerOfTwo

Finds the nearest power of two greater or equal to the given value.

Type signature

(x: number) => number

Examples

ceilToNearestPowerOfTwo(345);
// ⇒ 512

Try in REPL

Questions

How to get the nearest power of two greater or equal to the given value?

TypeScript source • JavaScript source

☰std/math/clamp

Clamps the given value to the given range.

Type signature

(min: number, max: number) => ((x: number) => number)

Examples

clamp(0, 10)(5);
// ⇒ 5

Try in REPL

clamp(0, 10)(-5);
// ⇒ 0

Try in REPL

clamp(0, 10)(15);
// ⇒ 10

Try in REPL

Questions

How to clamp value to the desired range?
How to enforce a value to be in a given range?

TypeScript source • JavaScript source

☰std/math/clampNormal

Clamps the given value to the [0, 1] range.

Type signature

(x: number) => number

Examples

clampNormal(0.5);
// ⇒ 0.5

Try in REPL

clampNormal(-0.5);
// ⇒ 0

Try in REPL

clampNormal(1.5);
// ⇒ 1

Try in REPL

Questions

How to clamp value to be in 0 to 1 inclusive range?
How to clamp value to be in the normal range?

TypeScript source • JavaScript source

☰std/math/clampPercentage

Clamps the given value to the [0, 100] range.

Type signature

(x: number) => number

Examples

clampPercentage(50);
// ⇒ 50

Try in REPL

clampPercentage(-50);
// ⇒ 0

Try in REPL

clampPercentage(150);
// ⇒ 100

Try in REPL

Questions

How to enforce a percentage be between 0% and 100%?

TypeScript source • JavaScript source

☰std/math/delta

Calculates the absolute distance between given values.

Type signature

(a: number, b: number) => number

Examples

delta(-3, 5);
// ⇒ 8

Try in REPL

Questions

How to calculate an absolute distance between two numbers?

TypeScript source • JavaScript source

☰std/math/inRectangleRange

Checks if the given value is in the rectangular range of [0, width] and [0, height]

Type signature

(width: number, height: number) => ((x: number, y: number) => boolean)

Examples

inRectangleRange(50, 100)(25, 50);
// ⇒ true

Try in REPL

inRectangleRange(50, 100)(-25, 50);
// ⇒ false

Try in REPL

Questions

How to check if a point is inside a rectangle defined by width and height?

TypeScript source • JavaScript source

☰std/math/lerp

Linearly interpolates two given values by the normal value of their distance.

Type signature

(t: number) => ((a: number, b: number) => number)

Examples

lerp(0.5)(0, 10);
// ⇒ 5

Try in REPL

lerp(0)(0, 10);
// ⇒ 0

Try in REPL

lerp(1)(0, 10);
// ⇒ 10

Try in REPL

Questions

How to linearly interpolate between two values?
How to interpolate two numbers?

TypeScript source • JavaScript source

☰std/math/maximumBy

Calculates the maximum by a given selector.

Type signature

(f: (x: number) => number) => ((xs: number[]) => number)

Examples

maximumBy(({ age }) => age)([
  { age: 13 },
  { age: 20 },
  { age: 7 },
  { age: 18 },
]);
// ⇒ { age: 20 }

Try in REPL

Questions

How to find a maximum element by a given function?

TypeScript source • JavaScript source

☰std/math/median

Calculates the median of the values. If there is an even number of items, the average of the middle ones is returned.

Type signature

(xs?: number[]) => number | undefined

Examples

median([-5, 3, 2, 29, 43]);
// ⇒ 3

Try in REPL

Questions

How to compute a median of an array?

TypeScript source • JavaScript source

☰std/math/minMax

Calculates the minimum and maximum value of the two given values.

Type signature

([a, b]: [number, number]) => [number, number]

Examples

minMax([5, 3]);
// ⇒ [3, 5]

Try in REPL

minMax([3, 5]);
// ⇒ [3, 5]

Try in REPL

Questions

How to get ordered values where the lower is the first and the higher is the second?

TypeScript source • JavaScript source

☰std/math/sameSign

Checks if all the given values have the same sign.

Type signature

(xs: number[]) => boolean

Examples

sameSign([-1, -2, -3]);
// ⇒ true

Try in REPL

sameSign([1, 2, -3]);
// ⇒ false

Try in REPL

Questions

How to check if all values have the same sign?

TypeScript source • JavaScript source

☰std/math/sign

Calculates the sign of the value and returns -1 for negative values, 1 for positive values and 0 for zeros.

Type signature

(x: number) => number

Examples

sign(3);
// ⇒ 1

Try in REPL

sign(-5);
// ⇒ 5

Try in REPL

sign(0);
// ⇒ 0

Try in REPL

sign(-0);
// ⇒ 0

Try in REPL

Questions

How to get a sign of a number?

TypeScript source • JavaScript source

☰std/math/standardDeviation

Calculates the standard deviation of the given array of numbers.

Type signature

(xs: number[], origin?: number) => number

Examples

standardDeviation([
  96, 81, 68, 79, 23, 13, 13, 59,
  44, 86,
]);
// ⇒ (2 * Math.sqrt(10922 / 5)) / 3

Try in REPL

Questions

How to compute a standard deviation of an array?

TypeScript source • JavaScript source

☰std/math/subtract

Subtracts two values.

Type signature

(a: number, b: number) => number

Examples

subtract(3, 5);
// ⇒ -2

Try in REPL

Questions

How to subtract two numbers?

TypeScript source • JavaScript source

object

☰std/object/any

Checks if the given object is present and it is not empty (contains at least one entry).

Type signature

<T>(xs?: GenericObject<T>) => boolean

Examples

any({ a: 1, b: 2, c: 3 });
// ⇒ true

Try in REPL

any({});
// ⇒ false

Try in REPL

any(null);
// ⇒ false

Try in REPL

any(undefined);
// ⇒ false

Try in REPL

Questions

How to check if an object is not empty?
How to check if an object contains some values?
How to check if an object is not null or undefined?

TypeScript source • JavaScript source

☰std/object/apply

Applies the given parameters to the given dictionary of functions.

Type signature

<T>(fs: {
    [index: string]: (...xs: T[]) => T;
}) => (...xs: T[]) => GenericObject<T>

Examples

const lower = (text) =>
  text.toLowerCase();
const upper = (text) =>
  text.toUpperCase();

apply({ lower, upper })("TeSt");
// ⇒ { lower: "test", upper: "TEST" }

Try in REPL

Questions

How to apply a value over an object of functions?

TypeScript source • JavaScript source

☰std/object/empty

Empty object.

Type signature

GenericObject<unknown>;
export default empty

Examples

empty;
// ⇒ {}

Try in REPL

Questions

How to get an empty object?

TypeScript source • JavaScript source

☰std/object/entries

Lists key-value pairs (entries) present in the given object.

Type signature

ObjectEntries

Examples

entries({ a: 1, b: 2, c: 3 });
// ⇒ [["a", 1], ["b", 2], ["c", 3]]

Try in REPL

Questions

How to get entries of an object?
How to get an array of key-value pairs of an object?

TypeScript source • JavaScript source

☰std/object/enumerable

Creates a 1 to 1 mapping of the given values as an object.

Type signature

(...xs: string[]) => object

Examples

enumerable("TEST", "X", "Y");
// ⇒ { TEST: 'TEST', X: 'X', Y: 'Y' }

Try in REPL

Questions

How to create an object of the same keys and values?

TypeScript source • JavaScript source

☰std/object/equals

Checks if two objects are deeply equal.

Type signature

(a: unknown, b: unknown) => boolean;
export default equalsDeep

Examples

equals({ a: 1 }, { a: 1 });
// ⇒ true

Try in REPL

equals(
  { b: [1, 2] },
  { b: [1, 2] },
);
// ⇒ true

Try in REPL

Questions

How to check if two objects are equal?
How to check deep object equality?

TypeScript source • JavaScript source

☰std/object/every

Test if every element passes the given predicate.

Type signature

<T>(f: (value: T, key: string, context: object) => boolean) => (xs: GenericObject<T>) => boolean

Examples

every((x) => x >= 0)({
  x: 5,
  y: 3,
  z: 0,
});
// ⇒ true

Try in REPL

every((x) => x > 0)({
  x: 5,
  y: 3,
  z: 0,
});
// ⇒ false

Try in REPL

Questions

How to check if every entry in an object passes a given predicate?

TypeScript source • JavaScript source

☰std/object/filter

Filters the given object with the given predicate.

Type signature

<T>(f: (value: T, key: string, context: object) => boolean) => (xs: GenericObject<T>) => GenericObject<T>

Examples

filter((x) => x % 2 !== 0)({
  a: 1,
  b: 2,
  c: 3,
});
// ⇒ { a: 1, c: 3 }

Try in REPL

Questions

How to filter an object?

TypeScript source • JavaScript source

☰std/object/find

Searches the given object by the given predicate and returns the found value or undefined.

Type signature

<T>(predicate: (value: T, key: string, context: object) => boolean) => (xs: GenericObject<T>) => T | undefined

Examples

find(({ x }) => x % 2 === 0)({
  a: { x: 1 },
  b: { x: 2 },
  c: { x: 3 },
});
// ⇒ { x: 2 }

Try in REPL

Questions

How to find the value of an object by a predicate function?

TypeScript source • JavaScript source

☰std/object/findEntry

Searches the given object by the given predicate and returns the found entry or undefined.

Type signature

<T>(predicate: (value: T, key: string, context: GenericObject<T>) => boolean) => (xs: GenericObject<T>) => [string, T] | undefined

Examples

findEntry(({ x }) => x % 2 === 0)({
  a: { x: 1 },
  b: { x: 2 },
  c: { x: 3 },
});
// ⇒ ["b", { x: 2 }]

Try in REPL

Questions

How to find an entry of an object by a predicate function?

TypeScript source • JavaScript source

☰std/object/findKey

Searches the given object by the given predicate and returns the found key or undefined.

Type signature

<T>(predicate: (value: T, key: string, context: object) => boolean) => (xs: GenericObject<T>) => string | undefined

Examples

findKey(({ x }) => x % 2 === 0)({
  a: { x: 1 },
  b: { x: 2 },
  c: { x: 3 },
});
// ⇒ "b"

Try in REPL

Questions

How to find a key of an object by a predicate function?

TypeScript source • JavaScript source

☰std/object/first

Returns the first value in the given object. Follows the default object iteration order.

Type signature

<T>(xs: GenericObject<T>) => T | undefined

Examples

first({ a: 1, b: 2, c: 3 });
// ⇒ 1

Try in REPL

Questions

How to get the first value of an object?

TypeScript source • JavaScript source

☰std/object/flatMapValues

Flat maps the values of the given object.

Type signature

<T, TResult>(f: (value: T, key: string, context: GenericObject<T>) => TResult[]) => (xs: GenericObject<T>) => TResult[]

Examples

flatMapValues((x) => [x, x * 2])({
  a: 1,
  b: 2,
  c: 3,
});
// ⇒ [1, 2, 2, 4, 3, 6]

Try in REPL

Questions

How to flat map an object?

TypeScript source • JavaScript source

☰std/object/fromEntries

Creates an object from an array of key-value pairs (entries).

Type signature

<T>(entries: [string, T][]) => Result<T>

Examples

fromEntries([
  ["a", 1],
  ["b", 2],
  ["c", 3],
]);
// ⇒ { a: 1, b: 2, c: 3 }

Try in REPL

Questions

How to create an object from an array of key-value pairs?
How to create an object from an array of entries?

TypeScript source • JavaScript source

☰std/object/groupBy

Groups the given array of values by the given key selector.

Type signature

(selector: (x: unknown) => string) => (xs: unknown[]) => Result

Examples

groupBy((x) =>
  x % 2 == 0 ? "even" : "odd",
)([1, 2, 3, 4, 5, 6, 7]);
// ⇒ { even: [2, 4, 6], odd: [1, 3, 5, 7] }

Try in REPL

Questions

How to group an array by a key function?

TypeScript source • JavaScript source

☰std/object/hasKey

Checks if the given key is present in the object.

Type signature

(key: string) => (xs?: unknown) => boolean

Examples

hasKey("c")({ a: 1, b: 2, c: 3 });
// ⇒ true

Try in REPL

Questions

How to check if an object contains a given key?

TypeScript source • JavaScript source

☰std/object/last

Returns the last value in the given object. Follows the default object iteration order.

Type signature

<T>(xs: GenericObject<T>) => T | undefined

Examples

last({ a: 1, b: 2, c: 3 });
// ⇒ 3

Try in REPL

Questions

How to get the last value of an object?

TypeScript source • JavaScript source

☰std/object/length

Returns the number of entries within the given object.

Type signature

<T>(xs: GenericObject<T>) => number

Examples

length({ a: 1, b: 2, c: 3 });
// ⇒ 3

Try in REPL

Questions

How to check how many entries are in an object?

TypeScript source • JavaScript source

☰std/object/map

Maps the given object with the given function.

Type signature

<T, TResult>(f: (value: T, key: string, context: object) => TResult) => (xs: GenericObject<T>) => GenericObject<TResult>

Examples

map((x) => x ** 2)({
  a: 1,
  b: 2,
  c: 3,
});
// ⇒ { a: 1, b: 4, c: 9 }

Try in REPL

Questions

How to map an object?
How to transform an object?

TypeScript source • JavaScript source

☰std/object/mapEntries

Maps entries of the given object.

Type signature

<T, TResult>(f: (value: T, key: string, context: object) => TResult) => (xs: GenericObject<T>) => [string, TResult][]

Examples

mapEntries((x) => x ** 2)({
  a: 1,
  b: 2,
  c: 3,
});
// ⇒ [["a", 1], ["b", 4], ["c", 9]]

Try in REPL

Questions

How to map object entries?

TypeScript source • JavaScript source

☰std/object/mapKeys

Transforms the object keys with the given function.

Type signature

<T>(f: (value: T, key: string, context: object) => string) => (xs: GenericObject<T>) => GenericObject<T>

Examples

mapKeys((_, key) =>
  key.toUpperCase(),
)({ a: 1, b: 2, c: 3 });
// ⇒ { A: 1, B: 2, C: 3 }

Try in REPL

Questions

How to map object keys?
How to transform object keys?

TypeScript source • JavaScript source

☰std/object/mapValues

Maps and returns an array of transformed object values.

Type signature

<T, TResult>(f: (value: T, key: string, context: object) => TResult) => (xs: GenericObject<T>) => TResult[]

Examples

mapValues((x) => x ** 2)({
  a: 1,
  b: 2,
  c: 3,
});
// ⇒ [1, 4, 9]

Try in REPL

Questions

How to map object values?

TypeScript source • JavaScript source

☰std/object/merge

Merges two objects deeply.

Type signature

(a: GenericObject, b: GenericObject) => GenericObject;
export default merge

Examples

merge({ a: 1, b: 3 }, {});
// ⇒ { a: 1, b: 3 }

Try in REPL

merge({ a: 1, b: 3 }, { b: 7 });
// ⇒ { a: 1, b: 7 }

Try in REPL

merge(
  { a: 1, b: 3 },
  { b: { d: 8 } },
);
// ⇒ { a: 1, b: { d: 8 } }

Try in REPL

merge(
  { a: 1, b: { c: 3 } },
  { b: { d: 8 } },
);
// ⇒ { a: 1, b: { c: 3, d: 8 } }

Try in REPL

Questions

How to merge two objects together?
How to deeply merge two objects?

TypeScript source • JavaScript source

☰std/object/none

Checks if the given object is empty.

Type signature

<T>(xs?: GenericObject<T>) => boolean

Examples

none({});
// ⇒ true

Try in REPL

none(null);
// ⇒ true

Try in REPL

none({ a: 1 });
// ⇒ false

Try in REPL

Questions

How to check if an object is empty?
How to check if an object is null or undefined?

TypeScript source • JavaScript source

☰std/object/some

Test if any element passes the given predicate.

Type signature

<T>(f: (value: T, key: string, context: object) => boolean) => (xs: GenericObject<T>) => boolean

Examples

some((x) => x >= 4)({
  x: 5,
  y: 3,
  z: 0,
});
// ⇒ true

Try in REPL

some((x) => x < 0)({
  x: 5,
  y: 3,
  z: 0,
});
// ⇒ false

Try in REPL

Questions

How to check if any entry in an object passes a given predicate?

TypeScript source • JavaScript source

☰std/object/sort

Sorts the given object by a comparator.

Type signature

<T>(f: (a: T, b: T) => number) => (xs: GenericObject<T>) => GenericObject<T>

Examples

sort({
  a: 3,
  b: 2,
  c: 3,
  d: -7,
  e: 13,
  f: 0,
  g: 8,
});
// ⇒ {"d": -7,"f": 0,"b": 2,"a": 3,"c": 3,"g": 8,"e": 13}

Try in REPL

Questions

How to sort an object?

TypeScript source • JavaScript source

query

☰std/query/parse

Parses a query string into an object.

Type signature

(xs?: string) => {
    [index: string]: string | boolean;
}

Examples

parse("test&count=5");
// ⇒ { test: true, count: "5" }

Try in REPL

Questions

How to parse a query string?

TypeScript source • JavaScript source

☰std/query/read

Parses the given query string into an object using URLSearchParams.

Type signature

(source: string) => Result

Examples

read("test&count=5");
// ⇒ { test: "", count: "5" }

Try in REPL

Questions

How to parse a query string using URLSearchParams?

TypeScript source • JavaScript source

☰std/query/serialize

Serializes the given object into a query string.

Type signature

<T>(xs?: GenericObject<T>) => string

Examples

serialize({
  test: true,
  value: "a string with spaces",
  missing: false,
});
// ⇒ "test&value=a%20string%20with%20spaces"

Try in REPL

Questions

How to serialize an object to a query string?

TypeScript source • JavaScript source

range

☰std/range/empty

Checks if the given range is empty.

Type signature

([min, max]: [number, number]) => boolean

Examples

empty([2, 2]);
// ⇒ true

Try in REPL

empty([1, 5]);
// ⇒ false

Try in REPL

Questions

How to check if a given range is empty (0-length)?

TypeScript source • JavaScript source

☰std/range/equals

Checks if the given ranges are equal.

Type signature

([a, b]: [number, number], [c, d]: [number, number]) => boolean

Examples

equals([1, 2], [1, 2]);
// ⇒ true

Try in REPL

equals([4, 3], [1, 2]);
// ⇒ false

Try in REPL

Questions

How to check if two ranges are equal?

TypeScript source • JavaScript source

☰std/range/length

Computes the signed length of the given range.

Type signature

([min, max]: [number, number]) => number

Examples

length([3, 15]);
// ⇒ 12

Try in REPL

length([1, 0]);
// ⇒ -1

Try in REPL

Questions

How to compute a signed length of a range?

TypeScript source • JavaScript source

☰std/range/split

Splits the given range into subranges by excluding the given used ranged.

Type signature

(used: [number, number][], sourceRange?: number[]) => (range: [number, number]) => [number, number][];
export default split

Examples

split([
  [2, 3],
  [5, 7],
]);
// ⇒ [[0, 2], [3, 5], [7, 10]]

Try in REPL

Questions

How to split a range into subranges?

TypeScript source • JavaScript source

regex

☰std/regex/escape

Escapes regex string into proper regex.

Type signature

(string: string) => string

Examples

escape("te.t").test("text");
// ⇒ false

Try in REPL

Questions

How to properly escape a regex string?

TypeScript source • JavaScript source

string

☰std/string/containsWhitespace

Checks if the given string contains whitespace.

Type signature

(x: string) => boolean

Examples

containsWhitespace("test string");
// ⇒ true

Try in REPL

containsWhitespace("test");
// ⇒ false

Try in REPL

Questions

How to check if a string contains whitespace?

TypeScript source • JavaScript source

☰std/string/empty

Empty string.

Type signature

""

Examples

empty();
// ⇒ ""

Try in REPL

Questions

How to get an empty string?

TypeScript source • JavaScript source

☰std/string/firstToLower

Transforms the first character to lowercase.

Type signature

(text: string) => string

Examples

firstToLower("TeSt");
// ⇒ "teSt"

Try in REPL

Questions

How to make the first letter of a string lowercase?

TypeScript source • JavaScript source

☰std/string/firstToUpper

Transforms the first character to uppercase.

Type signature

(text: string) => string

Examples

firstToUpper("teSt");
// ⇒ "TeSt"

Try in REPL

Questions

How to make the first letter of a string uppercase?

TypeScript source • JavaScript source

☰std/string/includes

Checks if the given substring is present in the source string.

Type signature

(search: string) => (text: string) => boolean

Examples

includes("brown fox")(
  "The quick brown fox jumps over the lazy dog",
);
// ⇒ true

Try in REPL

includes("brown dog")(
  "The quick brown fox jumps over the lazy dog",
);
// ⇒ false

Try in REPL

Questions

How to check if a string contains a given substring?

TypeScript source • JavaScript source

☰std/string/nbsp

Non-breaking space.

Type signature

" "

Examples

nbsp;
// ⇒ " "

Try in REPL

Questions

How to get a non-breaking space?

TypeScript source • JavaScript source

☰std/string/nonEmpty

Checks if the given string is present and is not empty or all whitespace.

Type signature

(x?: string) => boolean

Examples

nonEmpty("test with spaces");
// ⇒ true

Try in REPL

nonEmpty("   ");
// ⇒ false

Try in REPL

nonEmpty(null);
// ⇒ false

Try in REPL

Questions

How to check if a string is non-empty?
How to check if a string is not all whitespace?
How to check if a string is not null or undefined?

TypeScript source • JavaScript source

☰std/string/startsWith

Checks if the given string starts with the given substring.

Type signature

(prefix: string) => (xs: string) => boolean

Examples

startsWith("The")(
  "The quick brown fox jumps over the lazy dog",
);
// ⇒ true

Try in REPL

startsWith("Quick")(
  "The quick brown fox jumps over the lazy dog",
);
// ⇒ false

Try in REPL

Questions

How to check if a string starts with a given substring?

TypeScript source • JavaScript source

vector2

☰std/vector2/add

Adds two vectors.

Type signature

([x1, y1]: [number, number], [x2, y2]: [number, number]) => [number, number]

Examples

add([3, 5], [-1, 8]);
// ⇒ [2, 13]

Try in REPL

Questions

How to add two vectors?

TypeScript source • JavaScript source

☰std/vector2/convertSpace

Applies transformations to the given vector.

Type signature

(space: {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}) => ([x, y]: [number, number]) => number[]

Examples

convertSpace(rotate(Math.PI))([
  2, 3,
]);
// ⇒ [-2, -3]

Try in REPL

Questions

How to transform a vector with a matrix?

TypeScript source • JavaScript source

☰std/vector2/cross

Calculates a cross product of the given vectors. Returns a scalar.

Type signature

([a, b]: [number, number], [c, d]: [number, number]) => number

Examples

cross([3, 5], [-1, 8]);
// ⇒ 29

Try in REPL

cross([3, 5], [-1, -8]);
// ⇒ -19

Try in REPL

Questions

How to compute a cross product of two vectors?
How to check on which side of a line a point is?

TypeScript source • JavaScript source

☰std/vector2/dot

Calculates a dot product of the given vectors. Returns a scalar.

Type signature

([a, b]: [number, number], [c, d]: [number, number]) => number

Examples

dot([3, 5], [-1, 8]);
// ⇒ 37

Try in REPL

dot([3, 5], [-1, -8]);
// ⇒ -43

Try in REPL

Questions

How to compute a dot product of two vectors?

TypeScript source • JavaScript source

☰std/vector2/length

Calculates the length/magnitude of the given vector.

Type signature

([x, y]: [number, number]) => number

Examples

length([3, 5]);
// ⇒ Math.sqrt(3 * 3 + 5 * 5)

Try in REPL

Questions

How to compute the length of a vector?
How to compute the magnitude of a vector?

TypeScript source • JavaScript source

☰std/vector2/mul

Applies matrix transformation to the given vector.

Type signature

({ a, b, c, d, e, f }: {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}, [x, y]: [number, number]) => number[]

Examples

mul(scale(4, 5), [2, 3]);
// ⇒ [8, 15]

Try in REPL

Questions

How to apply a matrix transformation to a vector?

TypeScript source • JavaScript source

☰std/vector2/multiply

Multiples two matrices.

Type signature

(m1: {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}, m2: {
    a: number;
    b: number;
    c: number;
    d: number;
    e: number;
    f: number;
}) => {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}

Examples

multiply(
  {
    a: 1,
    c: 2,
    e: 3,
    b: 4,
    d: 5,
    f: 6,
  },
  {
    a: 7,
    c: 8,
    e: 9,
    b: 10,
    d: 11,
    f: 12,
  },
);
// ⇒ { a: 27, b: 78, c: 30, d: 87, e: 36, f: 102 }

Try in REPL

Questions

How to multiply two matrices?

TypeScript source • JavaScript source

☰std/vector2/normalize

Normalizes the given vector. Returns [0, 0] vector for points.

Type signature

(vector: [number, number]) => [number, number]

Examples

normalize([2, 3]);
// ⇒ [2 / length([2, 3]), 3 / length([2, 3])]

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Questions

How to normalize a vector?

TypeScript source • JavaScript source

☰std/vector2/reflect

Reflects the given vector on the given surface.

Type signature

(a: [number, number], v: [number, number]) => [number, number]

Examples

reflect([1, -2], [1, 0]);
// ⇒ [0.6, 0.8]

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Questions

How to reflect a vector on another vector?

TypeScript source • JavaScript source

☰std/vector2/rotate

Creates a rotation matrix around given origin [0, 0] by default.

Type signature

(angle?: number, cx?: number, cy?: number) => {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}

Examples

const angle = Math.PI;
const sine = Math.sin(angle);
const cosine = Math.cos(angle);

rotate(angle); // { a: cosine, b: sine, c: -sine, d: cosine, e: 0, f: 0 }

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Questions

How to create a rotation matrix?

TypeScript source • JavaScript source

☰std/vector2/scale

Creates a scale matrix.

Type signature

(sx?: number, sy?: number) => {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}

Examples

scale(2, 3);
// ⇒ { a: 2, b: 0, c: 0, d: 3, e: 0, f: 0 }

Try in REPL

Questions

How to create a scale matrix?

TypeScript source • JavaScript source

☰std/vector2/sub

Subtracts two vectors.

Type signature

([x1, y1]: [number, number], [x2, y2]: [number, number]) => [number, number]

Examples

sub([3, 5], [-1, 8]);
// ⇒ [4, -3]

Try in REPL

Questions

How to subtract two vectors?

TypeScript source • JavaScript source

☰std/vector2/transform

Composes a single transformation by matrix multiplication.

Type signature

(...matrices: {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}[]) => {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}

Examples

const originX = 5;
const originY = 6;
const angle = Math.PI;

transform(
  translate(originX, originY),
  rotate(angle),
  translate(-originX, -originY),
);
// ⇒ rotate(Math.PI, originX, originY)

Try in REPL

Questions

How to compose multiple matrix transformations into a single matrix?

TypeScript source • JavaScript source

☰std/vector2/translate

Creates a translation matrix.

Type signature

(tx?: number, ty?: number) => {
    a: number;
    c: number;
    e: number;
    b: number;
    d: number;
    f: number;
}

Examples

translate(2, 3);
// ⇒ { a: 1, b: 0, c: 0, d: 1, e: 2, f: 3 }

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Questions

How to create a translation matrix?

TypeScript source • JavaScript source

web

☰std/web/classNames

Composes class name from truthy values with the support of string and objects.

Type signature

(...xs: unknown[]) => string

Examples

classNames("test", {
  active: true,
  disabled: false,
  on: undefined,
});
// ⇒ "test active"

Try in REPL

Questions

How to create a class name from an array of strings and/or objects?

TypeScript source • JavaScript source

events

☰std/web/events/cancel

Stops propagation and prevents the default handler of the given event.

Type signature

(event: {
    preventDefault: () => void;
    stopPropagation: () => void;
}) => boolean

Examples

const event = {
  preventDefault: () =>
    console.log("preventDefault"),
  stopPropagation: () =>
    console.log("stopPropagation"),
};

cancel(event);

Try in REPL

Questions

How to stop event propagation and prevent default at once?

TypeScript source • JavaScript source

☰std/web/events/openInNewTabIntent

Tests if the current event seems like an intent to open a new tab. Useful for client-side navigation handling.

Type signature

({ button, ctrlKey, metaKey, shiftKey }: {
    button?: number;
    ctrlKey?: boolean;
    metaKey?: boolean;
    shiftKey?: boolean;
}) => boolean

Examples

openInNewTabIntent({
  ctrlKey: true,
});
// ⇒ true

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Questions

How to check if the user wants to open a new tab using history API?

TypeScript source • JavaScript source

☰std/web/events/prevent

Prevents the default handler of the given event.

Type signature

(event: {
    preventDefault: () => void;
}) => boolean

Examples

const event = {
  preventDefault: () =>
    console.log("preventDefault"),
  stopPropagation: () =>
    console.log("stopPropagation"),
};

prevent(event);

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Questions

How to prevent default event handler?

TypeScript source • JavaScript source

☰std/web/events/stop

Stops propagation of the given event.

Type signature

(event: {
    stopPropagation: () => void;
}) => boolean

Examples

const event = {
  preventDefault: () =>
    console.log("preventDefault"),
  stopPropagation: () =>
    console.log("stopPropagation"),
};

stop(event);

Try in REPL

Questions

How to stop the propagation of an event?

TypeScript source • JavaScript source

☰std/array/any

Type signature

Examples

Questions

☰std/array/are

Type signature

Examples

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☰std/array/chunk

Type signature

Examples

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☰std/array/difference

Type signature

Examples

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☰std/array/differs

Type signature

Examples

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☰std/array/duplicates

Type signature

Examples

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☰std/array/empty

Type signature

Examples

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☰std/array/exact

Type signature

Examples

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☰std/array/except

Type signature

Examples

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☰std/array/filterInPlace

Type signature

Examples

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☰std/array/find

Type signature

Examples

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☰std/array/first

Type signature

Examples

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☰std/array/flatMap

Type signature

Examples

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☰std/array/flatten

Type signature

Examples

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☰std/array/insert

Type signature

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☰std/array/intersection

Type signature

Examples

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☰std/array/is

Type signature

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☰std/array/last

Type signature

Examples

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☰std/array/length

Type signature

Examples

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☰std/array/lengthDiffers

Type signature

Examples

Questions