API / Belt / Array

Array

Utililites for Array functions.

Note about index syntax

Code like arr[0] does not compile to JavaScript arr[0]. Reason transforms the [] index syntax into a function: Array.get(arr, 0). By default, this uses the default standard library's Array.get function, which may raise an exception if the index isn't found. If you open Belt, it will use the Belt.Array.get function which returns options instead of raising exceptions. See this for more information.

t

RESCRIPT

type t<'a> = array<'a>

length

RESCRIPT

let length: t<'a> => int

Return the size of the array

Examples

RESCRIPT
// Returns 1
Belt.Array.length(["test"])

size

RESCRIPT

let size: t<'a> => int

See Belt.Array.length

get

RESCRIPT

let get: (t<'a>, int) => option<'a>

If i <= 0 <= length(arr) returns Some(value) where value is the item at index i. If i is out of range returns None.

Examples

RESCRIPT
Belt.Array.get(["a", "b", "c"], 0) == Some("a")
Belt.Array.get(["a", "b", "c"], 3) == None
Belt.Array.get(["a", "b", "c"], -1) == None

getExn

RESCRIPT

let getExn: (t<'a>, int) => 'a

Raise an exception if i is out of range. Otherwise return the value at index i in arr.

getUnsafe

RESCRIPT

let getUnsafe: (t<'a>, int) => 'a

getUnsafe(arr, i)

Unsafe

no bounds checking; this would cause type error if i does not stay within range

getUndefined

RESCRIPT

let getUndefined: (t<'a>, int) => Js.undefined<'a>

getUndefined(arr, i)

It does the samething in the runtime as getUnsafe; it is type safe since the return type still track whether it is in range or not

set

RESCRIPT

let set: (t<'a>, int, 'a) => bool

set(arr, n, x) modifies arr in place; it replaces the nth element of arr with x. Returning false means not updated due to out of range.

setExn

RESCRIPT

let setExn: (t<'a>, int, 'a) => unit

setExn(arr, i, x) raise an exception if i is out of range.

setUnsafe

RESCRIPT

let setUnsafe: (t<'a>, int, 'a) => unit

shuffleInPlace

RESCRIPT

let shuffleInPlace: t<'a> => unit

shuffleInPlace(arr) randomly re-orders the items in arr

shuffle

RESCRIPT

let shuffle: t<'a> => t<'a>

Returns a fresh array with items in original array randomly shuffled.

reverseInPlace

RESCRIPT

let reverseInPlace: t<'a> => unit

reverseInPlace(arr) reverses items in arr in place.

Examples

RESCRIPT
let arr = [10, 11, 12, 13, 14]

let () = Belt.Array.reverseInPlace(arr)

arr == [14, 13, 12, 11, 10]

reverse

RESCRIPT

let reverse: t<'a> => t<'a>

reverse(arr) returns a fresh array with items in arr in reverse order.

Examples

RESCRIPT
Belt.Array.reverse([10, 11, 12, 13, 14]) == [14, 13, 12, 11, 10]

makeUninitialized

RESCRIPT

let makeUninitialized: int => array<Js.undefined<'a>>

makeUninitialized(n) creates an array of length n filled with the undefined value. You must specify the type of data that will eventually fill the array.

Examples

RESCRIPT
let arr: array<Js.undefined<string>> = Belt.Array.makeUninitialized(5)

Belt.Array.getExn(arr, 0) == Js.undefined

makeUninitializedUnsafe

RESCRIPT

let makeUninitializedUnsafe: int => t<'a>

Unsafe

Examples

RESCRIPT
let arr = Belt.Array.makeUninitializedUnsafe(5)

Js.log(Belt.Array.getExn(arr, 0)) // undefined

Belt.Array.setExn(arr, 0, "example")

Js.log(Belt.Array.getExn(arr, 0) == "example")

make

RESCRIPT

let make: (int, 'a) => t<'a>

make(n, e) return an array of size n filled with value e. Returns an empty array when n is negative.

range

RESCRIPT

let range: (int, int) => array<int>

range(start, finish) create an inclusive array.

Examples

RESCRIPT
Belt.Array.range(0, 3) == [0, 1, 2, 3]

Belt.Array.range(3, 0) == []

Belt.Array.range(3, 3) == [3]

rangeBy

RESCRIPT

let rangeBy: (int, int, ~step: int) => array<int>

rangeBy(start, finish, ~step) returns empty array when step is 0 or negative. It also return an empty array when start > finish.

Examples

RESCRIPT
Belt.Array.rangeBy(0, 10, ~step=3) == [0, 3, 6, 9]

Belt.Array.rangeBy(0, 12, ~step=3) == [0, 3, 6, 9, 12]

Belt.Array.rangeBy(33, 0, ~step=1) == []

Belt.Array.rangeBy(33, 0, ~step=-1) == []

Belt.Array.rangeBy(3, 12, ~step=-1) == []

Belt.Array.rangeBy(3, 3, ~step=0) == []

Belt.Array.rangeBy(3, 3, ~step=1) == [3]

makeByU

RESCRIPT

let makeByU: (int, (. int) => 'a) => t<'a>

makeBy

RESCRIPT

let makeBy: (int, int => 'a) => t<'a>

makeBy(n, f) return an empty array when n is negative return an array of size n populated by f(i) start from 0 to n - 1.

Examples

RESCRIPT
Belt.Array.makeBy(5, (i) => i) == [0, 1, 2, 3, 4]

Belt.Array.makeBy(5, (i) => i * i) == [0, 1, 4, 9, 16]

makeByAndShuffleU

RESCRIPT

let makeByAndShuffleU: (int, (. int) => 'a) => t<'a>

makeByAndShuffle

RESCRIPT

let makeByAndShuffle: (int, int => 'a) => t<'a>

Equivalent to shuffle(makeBy(n, f))

zip

RESCRIPT

let zip: (t<'a>, array<'b>) => array<('a, 'b)>

zip(a, b) create an array of pairs from corresponding elements of a and b. Stop with the shorter array.

Examples

RESCRIPT
Belt.Array.zip([1, 2], [3, 4, 5]) == [(1, 3), (2, 4)]

zipByU

RESCRIPT

let zipByU: (t<'a>, array<'b>, (. 'a, 'b) => 'c) => array<'c>

zipBy

RESCRIPT

let zipBy: (t<'a>, array<'b>, ('a, 'b) => 'c) => array<'c>

zipBy(xs, ys, f) create an array by applying f to corresponding elements of xs and ys. Stops with shorter array.

Equivalent to map(zip(xs, ys), ((a, b)) => f(a, b))

Examples

RESCRIPT
Belt.Array.zipBy([1, 2, 3], [4, 5], (a, b) => 2 * a + b) == [6, 9]

unzip

RESCRIPT

let unzip: array<('a, 'b)> => (t<'a>, array<'b>)

unzip(a) takes an array of pairs and creates a pair of arrays. The first array contains all the first items of the pairs; the second array contains all the second items.

Examples

RESCRIPT
Belt.Array.unzip([(1, 2), (3, 4)]) == ([1, 3], [2, 4])

Belt.Array.unzip([(1, 2), (3, 4), (5, 6), (7, 8)]) == ([1, 3, 5, 7], [2, 4, 6, 8])

concat

RESCRIPT

let concat: (t<'a>, t<'a>) => t<'a>

concat(xs, ys) returns a fresh array containing the concatenation of the arrays v1 and v2, so even if v1 or v2 is empty; it can not be shared.

Examples

RESCRIPT
Belt.Array.concat([1, 2, 3], [4, 5]) == [1, 2, 3, 4, 5]

Belt.Array.concat([], ["a", "b", "c"]) == ["a", "b", "c"]

concatMany

RESCRIPT

let concatMany: array<t<'a>> => t<'a>

concatMany(xss) returns a fresh array as the concatenation of xss (an array of arrays)

Examples

RESCRIPT
Belt.Array.concatMany([[1, 2, 3], [4, 5, 6], [7, 8]]) == [1, 2, 3, 4, 5, 6, 7, 8]

slice

RESCRIPT

let slice: (t<'a>, ~offset: int, ~len: int) => t<'a>

slice(xs, offset, len) creates a new array with the len elements of xs starting at offset for offset can be negative;and is evaluated as length(xs) - offset(slice, xs) - 1(1) means get the last element as a singleton array slice(xs, ~-len, len) will return a copy of the array if the array does not have enough data; slice extracts through the end of sequence.

if len is negative; returns the empty array.

Examples

RESCRIPT
Belt.Array.slice([10, 11, 12, 13, 14, 15, 16], ~offset=2, ~len=3) == [12, 13, 14]

Belt.Array.slice([10, 11, 12, 13, 14, 15, 16], ~offset=-4, ~len=3) == [13, 14, 15]

Belt.Array.slice([10, 11, 12, 13, 14, 15, 16], ~offset=4, ~len=9) == [14, 15, 16]

sliceToEnd

RESCRIPT

let sliceToEnd: (t<'a>, int) => t<'a>

sliceToEnd(xs, offset) creates a new array with the elements of xs starting at offset

offset can be negative; and is evaluated as length(xs) - offset(sliceToEnd, xs) - 1 means get the last element as a singleton array

sliceToEnd(xs, 0) will return a copy of the array

Examples

RESCRIPT
Belt.Array.sliceToEnd([10, 11, 12, 13, 14, 15, 16], 2) == [12, 13, 14, 15, 16]

Belt.Array.sliceToEnd([10, 11, 12, 13, 14, 15, 16], -4) == [13, 14, 15, 16]

copy

RESCRIPT

let copy: t<'a> => t<'a>

copy(a) returns a copy of a; that is; a fresh array containing the same elements as a.

fill

RESCRIPT

let fill: (t<'a>, ~offset: int, ~len: int, 'a) => unit

fill(arr, ~offset, ~len, x) modifies arr in place, storing x in elements number offset to offset + len - 1. offset can be negative; and is evaluated as length(arr - offset).

fill(arr, ~offset=-1, ~len=1) means fill the last element, if the array does not have enough data; fill will ignore it

Examples

RESCRIPT
let arr = Belt.Array.makeBy(5, (i) => i)

Belt.Array.fill(arr, ~offset=2, ~len=2, 9)

arr == [0, 1, 9, 9, 4]

Belt.Array.fill(arr, ~offset=7, ~len=2, 8)

arr == [0, 1, 9, 9, 4]

blit

RESCRIPT

let blit: (
  ~src: t<'a>,
  ~srcOffset: int,
  ~dst: t<'a>,
  ~dstOffset: int,
  ~len: int,
) => unit

blit(~src=v1, ~srcOffset=o1, ~dst=v2, ~dstOffset=o2, ~len) copies len elements from array v1;starting at element number o1;to array v2, starting at element number o2. It works correctly even if v1 and v2 are the same array and the source and destination chunks overlap.

offset can be negative; -1 means len - 1; if len + offset is still negative;it will be set as 0

For each of the examples;presume that v1 == [10, 11, 12, 13, 14, 15, 16, 17] and v2 == [20, 21, 22, 23, 24, 25, 26, 27]. The result shown is the content of the destination array.

Examples

RESCRIPT
let v1 = [10, 11, 12, 13, 14, 15, 16, 17]
let v2 = [20, 21, 22, 23, 24, 25, 26, 27]

Belt.Array.blit(~src=v1, ~srcOffset=4, ~dst=v2, ~dstOffset=2, ~len=3)
v2 == [20, 21, 14, 15, 16, 25, 26, 27]

Belt.Array.blit(~src=v1, ~srcOffset=4, ~dst=v1, ~dstOffset=2, ~len=3)
v1 == [10, 11, 14, 15, 16, 15, 16, 17]

blitUnsafe

RESCRIPT

let blitUnsafe: (
  ~src: t<'a>,
  ~srcOffset: int,
  ~dst: t<'a>,
  ~dstOffset: int,
  ~len: int,
) => unit

Unsafe blit without bounds checking.

forEachU

RESCRIPT

let forEachU: (t<'a>, (. 'a) => unit) => unit

forEach

RESCRIPT

let forEach: (t<'a>, 'a => unit) => unit

forEach(xs, f)

Call f on each element of xs from the beginning to end. f returns unit so no new array is created. Use forEach when you are primarily concerned with repetitively creating side effects.

Examples

RESCRIPT
Belt.Array.forEach(["a", "b", "c"], x => Js.log("Item: " ++ x))

/*
  prints:
  Item: a
  Item: b
  Item: c
*/
let total = ref(0)

Belt.Array.forEach([1, 2, 3, 4], x => total := total.contents + x)

total.contents == 1 + 2 + 3 + 4

mapU

RESCRIPT

let mapU: (t<'a>, (. 'a) => 'b) => array<'b>

map

RESCRIPT

let map: (t<'a>, 'a => 'b) => array<'b>

map(xs, f) returns a new array by calling f for each element of xs from the beginning to end.

Examples

RESCRIPT
Belt.Array.map([1, 2], (x) => x + 1) == [3, 4]

flatMapU

RESCRIPT

let flatMapU: (t<'a>, (. 'a) => array<'b>) => array<'b>

flatMap

RESCRIPT

let flatMap: (t<'a>, 'a => array<'b>) => array<'b>

flatMap(xs, f) returns a new array by calling f for each element of xs from the beginning to end, concatenating the results.

Examples

RESCRIPT
Belt.Array.flatMap([1, 2], x => [x + 10, x + 20]) == [11, 21, 12, 22]

getByU

RESCRIPT

let getByU: (t<'a>, (. 'a) => bool) => option<'a>

getBy

RESCRIPT

let getBy: (t<'a>, 'a => bool) => option<'a>

getBy(xs, p) returns Some(value) for the first value in xs that satisifies the predicate function p; returns None if no element satisifies the function.

Examples

RESCRIPT
Belt.Array.getBy([1, 4, 3, 2], (x) => mod(x, 2) == 0) == Some(4)
Belt.Array.getBy([15, 13, 11], (x) => mod(x, 2) == 0) == None

getIndexByU

RESCRIPT

let getIndexByU: (t<'a>, (. 'a) => bool) => option<int>

getIndexBy

RESCRIPT

let getIndexBy: (t<'a>, 'a => bool) => option<int>

getIndexBy(xs, p) returns Some(index) for the first value in xs that satisifies the predicate function p; returns None if no element satisifies the function.

Examples

RESCRIPT
Belt.Array.getIndexBy([1, 4, 3, 2], (x) => mod(x, 2) == 0) == Some(1)
Belt.Array.getIndexBy([15, 13, 11], (x) => mod(x, 2) == 0) == None

keepU

RESCRIPT

let keepU: (t<'a>, (. 'a) => bool) => t<'a>

keep

RESCRIPT

let keep: (t<'a>, 'a => bool) => t<'a>

keep(xs, p) returns a new array that keep all elements satisfy p.

keepWithIndexU

RESCRIPT

let keepWithIndexU: (t<'a>, (. 'a, int) => bool) => t<'a>

keepWithIndex

RESCRIPT

let keepWithIndex: (t<'a>, ('a, int) => bool) => t<'a>

keepWithIndex(xs, p) returns a new array that keep all elements satisfy p.

Examples

RESCRIPT
Belt.Array.keepWithIndex([1, 2, 3], (_x, i) => i == 1) == [2]

keepMapU

RESCRIPT

let keepMapU: (t<'a>, (. 'a) => option<'b>) => array<'b>

keepMap

RESCRIPT

let keepMap: (t<'a>, 'a => option<'b>) => array<'b>

keepMap(xs, p) returns a new array that keep all elements that return a non None applied p.

Examples

RESCRIPT
Belt.Array.keepMap([1, 2, 3], x =>
  if mod(x, 2) == 0 {
    Some(x)
  } else {
    None
  }
)
== [2]

forEachWithIndexU

RESCRIPT

let forEachWithIndexU: (t<'a>, (. int, 'a) => unit) => unit

forEachWithIndex

RESCRIPT

let forEachWithIndex: (t<'a>, (int, 'a) => unit) => unit

forEachWithIndex(xs, f) same as Belt.Array.forEach, except that f is supplied two arguments: the index starting from 0 and the element from xs.

Examples

RESCRIPT
Belt.Array.forEachWithIndex(["a", "b", "c"], (i, x) => Js.log("Item " ++ Belt.Int.toString(i) ++ " is " ++ x))

/*
  prints:
  Item 0 is a
  Item 1 is b
  Item 2 is cc
*/
let total = ref(0)

Belt.Array.forEachWithIndex([10, 11, 12, 13], (i, x) => total := total.contents + x + i)

total.contents == 0 + 10 + 1 + 11 + 2 + 12 + 3 + 13

mapWithIndexU

RESCRIPT

let mapWithIndexU: (t<'a>, (. int, 'a) => 'b) => array<'b>

mapWithIndex

RESCRIPT

let mapWithIndex: (t<'a>, (int, 'a) => 'b) => array<'b>

mapWithIndex(xs, f) applies f to each element of xs. Function f takes two arguments: the index starting from 0 and the element from xs.

Examples

RESCRIPT
Belt.Array.mapWithIndex([1, 2, 3], (i, x) => i + x) == [0 + 1, 1 + 2, 2 + 3]

partitionU

RESCRIPT

let partitionU: (t<'a>, (. 'a) => bool) => (t<'a>, t<'a>)

partition

RESCRIPT

let partition: (t<'a>, 'a => bool) => (t<'a>, t<'a>)

partition(f, a) split array into tuple of two arrays based on predicate f; first of tuple where predicate cause true, second where predicate cause false

Examples

RESCRIPT
Belt.Array.partition([1, 2, 3, 4, 5], (x) => mod(x, 2) == 0) == ([2, 4], [1, 3, 5])

Belt.Array.partition([1, 2, 3, 4, 5], (x) => mod(x, 2) != 0) == ([1, 3, 5], [2, 4])

reduceU

RESCRIPT

let reduceU: (array<'b>, 'a, (. 'a, 'b) => 'a) => 'a

reduce

RESCRIPT

let reduce: (array<'b>, 'a, ('a, 'b) => 'a) => 'a

reduce(xs, init, f) applies f to each element of xs from beginning to end. Function f has two parameters: the item from the list and an “accumulator”; which starts with a value of init. reduce returns the final value of the accumulator.

Examples

RESCRIPT
Belt.Array.reduce([2, 3, 4], 1, (a, b) => a + b) == 10

Belt.Array.reduce(["a", "b", "c", "d"], "", (a, b) => a ++ b) == "abcd"

reduceReverseU

RESCRIPT

let reduceReverseU: (array<'b>, 'a, (. 'a, 'b) => 'a) => 'a

reduceReverse

RESCRIPT

let reduceReverse: (array<'b>, 'a, ('a, 'b) => 'a) => 'a

reduceReverse(xs, init, f) works like Belt.Array.reduce except that function f is applied to each item of xs from the last back to the first.

Examples

RESCRIPT
Belt.Array.reduceReverse(["a", "b", "c", "d"], "", (a, b) => a ++ b) == "dcba"

reduceReverse2U

RESCRIPT

let reduceReverse2U: (t<'a>, array<'b>, 'c, (. 'c, 'a, 'b) => 'c) => 'c

reduceReverse2

RESCRIPT

let reduceReverse2: (t<'a>, array<'b>, 'c, ('c, 'a, 'b) => 'c) => 'c

reduceReverse2(xs, ys, init, f) reduces two arrays xs and ys;taking items starting at min(length(xs), length(ys)) down to and including zero.

Examples

RESCRIPT
Belt.Array.reduceReverse2([1, 2, 3], [1, 2], 0, (acc, x, y) => acc + x + y) == 6

reduceWithIndexU

RESCRIPT

let reduceWithIndexU: (t<'a>, 'b, (. 'b, 'a, int) => 'b) => 'b

reduceWithIndex

RESCRIPT

let reduceWithIndex: (t<'a>, 'b, ('b, 'a, int) => 'b) => 'b

Applies f to each element of xs from beginning to end. Function f has three parameters: the item from the array and an “accumulator”, which starts with a value of init and the index of each element. reduceWithIndex returns the final value of the accumulator.

Examples

RESCRIPT
Belt.Array.reduceWithIndex([1, 2, 3, 4], 0, (acc, x, i) => acc + x + i) == 16

joinWithU

RESCRIPT

let joinWithU: (t<'a>, string, (. 'a) => string) => string

joinWith

RESCRIPT

let joinWith: (t<'a>, string, 'a => string) => string

joinWith(xs, sep, toString)

Concatenates all the elements of xs converted to string with toString, each separated by sep, the string given as the second argument, into a single string. If the array has only one element, then that element will be returned without using the separator. If the array is empty, the empty string will be returned.

Examples

RESCRIPT
Belt.Array.joinWith([0, 1], ", ", Js.Int.toString) == "0, 1"
Belt.Array.joinWith([], " ", Js.Int.toString) == ""
Belt.Array.joinWith([1], " ", Js.Int.toString) == "1"

someU

RESCRIPT

let someU: (t<'a>, (. 'a) => bool) => bool

some

RESCRIPT

let some: (t<'a>, 'a => bool) => bool

some(xs, p) returns true if at least one of the elements in xs satifies p; where p is a predicate: a function taking an element and returning a bool.

Examples

RESCRIPT
Belt.Array.some([2, 3, 4], (x) => mod(x, 2) == 1) == true

Belt.Array.some([(-1), (-3), (-5)], (x) => x > 0) == false

everyU

RESCRIPT

let everyU: (t<'a>, (. 'a) => bool) => bool

every

RESCRIPT

let every: (t<'a>, 'a => bool) => bool

every(xs, p) returns true if all elements satisfy p; where p is a predicate: a function taking an element and returning a bool.

Examples

RESCRIPT
Belt.Array.every([1, 3, 5], (x) => mod(x, 2) == 1) == true

Belt.Array.every([1, (-3), 5], (x) => x > 0) == false

every2U

RESCRIPT

let every2U: (t<'a>, array<'b>, (. 'a, 'b) => bool) => bool

every2

RESCRIPT

let every2: (t<'a>, array<'b>, ('a, 'b) => bool) => bool

every2(xs, ys, p) returns true if p(xi, yi) is true for all pairs of elements up to the shorter length (i.e. min(length(xs), length(ys)))

Examples

RESCRIPT
Belt.Array.every2([1, 2, 3], [0, 1], (a, b) => a > b) == true

Belt.Array.every2([], [1], (x, y) => x > y) == true

Belt.Array.every2([2, 3], [1], (x, y) => x > y) == true

Belt.Array.every2([0, 1], [5, 0], (x, y) => x > y) == false

some2U

RESCRIPT

let some2U: (t<'a>, array<'b>, (. 'a, 'b) => bool) => bool

some2

RESCRIPT

let some2: (t<'a>, array<'b>, ('a, 'b) => bool) => bool

some2(xs, ys, p) returns true if p(xi, yi) is true for any pair of elements up to the shorter length (i.e. min(length(xs), length(ys)))

Examples

RESCRIPT
Belt.Array.some2([0, 2], [1, 0, 3], (a, b) => a > b) == true

Belt.Array.some2([], [1], (x, y) => x > y) == false

Belt.Array.some2([2, 3], [1, 4], (x, y) => x > y) == true

cmpU

RESCRIPT

let cmpU: (t<'a>, t<'a>, (. 'a, 'a) => int) => int

cmp

RESCRIPT

let cmp: (t<'a>, t<'a>, ('a, 'a) => int) => int

cmp(xs, ys, f) compared by length if length(xs) != length(ys); returning -1 if length(xs) < length(ys) or 1 if length(xs) > length(ys). Otherwise compare one by one f(x, y). f returns a negative number if x is “less than” y zero if x is “equal to” y a positive number if x is “greater than” y. The comparison returns the first non-zero result of f; or zero if f returns zero for all x and y.

Examples

RESCRIPT
Belt.Array.cmp([1, 3, 5], [1, 4, 2], (a, b) => compare(a, b)) == -1

Belt.Array.cmp([1, 3, 5], [1, 2, 3], (a, b) => compare(a, b)) == 1

Belt.Array.cmp([1, 3, 5], [1, 3, 5], (a, b) => compare(a, b)) == 0

eqU

RESCRIPT

let eqU: (t<'a>, t<'a>, (. 'a, 'a) => bool) => bool

eq

RESCRIPT

let eq: (t<'a>, t<'a>, ('a, 'a) => bool) => bool

eq(xs, ys) return false if length is not the same otherwise compare items one by one using f(xi, yi); and return true if all results are true false otherwise

Examples

RESCRIPT
Belt.Array.eq([1, 2, 3], [(-1), (-2), (-3)], (a, b) => abs(a) == abs(b)) == true

truncateToLengthUnsafe

RESCRIPT

let truncateToLengthUnsafe: (t<'a>, int) => unit

Unsafe truncateToLengthUnsafe(xs, n) sets length of array xs to n. If n is greater than the length of xs; the extra elements are set to Js.Null_undefined.null. If n is less than zero; raises a RangeError.

Examples

RESCRIPT
let arr = ["ant", "bee", "cat", "dog", "elk"]

Belt.Array.truncateToLengthUnsafe(arr, 3)

arr == ["ant", "bee", "cat"]

initU

RESCRIPT

let initU: (int, (. int) => 'a) => t<'a>

init

RESCRIPT

let init: (int, int => 'a) => t<'a>

push

RESCRIPT

let push: (t<'a>, 'a) => unit

arr->push(item) pushes an element item into an array arr.