Array<T>.prototype.*

• concat(...items: (T | Array<T>)[]): T[]

  • Non-destructively concatenates this and the parameters (which can be single elements or array of elements).
  • ES3, non-destructive
  • ['a'].concat('b', ['c', 'd']) → [ 'a', 'b', 'c', 'd' ]

• copyWithin(target: number, start: number, end?: number): this

  • Copies the elements whose indices range from start to (excl.) end to indices starting with target. Overlapping is handled correctly.
  • ES6, destructive
  • ['a', 'b', 'c', 'd'].copyWithin(0, 2, 4) → [ 'c', 'd', 'c', 'd' ]

• entries(): Iterable<[number, T]>

  • Returns an iterable over [index, element] pairs.
  • ES6, non-destructive
  • Array.from(['a', 'b'].entries()) → [ [ 0, 'a' ], [ 1, 'b' ] ]

• every(callback: (value: T, index: number, array: Array<T>) => boolean, thisArg?: any): boolean

  • Returns true if callback returns true for every element. Stops as soon as it receives false. Math: ∀
  • ES5, non-destructive
  • [1, 2, 3].every(x => x > 0) → true
  • [1, -2, 3].every(x => x > 0) → false

• fill(value: T, start?: number, end?: number): this

  • Assigns value to every index.
  • ES6, destructive
  • [0, 1, 2].fill('a') → [ 'a', 'a', 'a' ]

• filter(callback: (value: T, index: number, array: Array<T>) => any, thisArg?: any): T[]

  • Returns an array with only those elements for which callback returns true.
  • ES5, non-destructive
  • [1, -2, 3].filter(x => x > 0) → [ 1, 3 ]

• find(predicate: (value: T, index: number, obj: T[]) => boolean, thisArg?: any): T | undefined

  • The result is the first element for which predicate returns true. If it never does, the result is undefined.
  • ES6, non-destructive
  • [1, -2, 3].find(x => x < 0) → -2
  • [1, 2, 3].find(x => x < 0) → undefined

• findIndex(predicate: (value: T, index: number, obj: T[]) => boolean, thisArg?: any): number

  • The result is the index of the first element for which predicate returns true. If it never does, the result is -1.
  • ES6, non-destructive
  • [1, -2, 3].findIndex(x => x < 0) → 1
  • [1, 2, 3].findIndex(x => x < 0) → -1

• forEach(callback: (value: T, index: number, array: Array<T>) => void, thisArg?: any): void

  • Calls callback for each element.
  • ES5, non-destructive
  • ['a', 'b'].forEach((x, i) => console.log(x, i))

• includes(searchElement: T, fromIndex?: number): boolean

  • Returns true if searchElement is an element and false, otherwise.
  • ES2016, non-destructive
  • [0, 1, 2].includes(1) -> true
  • [0, 1, 2].includes(5) -> false

• indexOf

• join

• keys

• lastIndexOf

• map

• pop

• push

• reduce

• reduceRight

• reverse

• shift

• slice

• some

• sort

• splice

• toLocaleString

• toString

• unshift

• values

How holes are handled is described in Sect. “Array operations and holes” in “Exploring ES6”.