Array<T>.prototype.*

• concat(...items: (T | Array<T>)[]): T[] 🔒
  • Returns a new array that is the concatenation of this and all items. Non-array parameters are treated as if they were arrays with single elements.
  • ES3
  • ['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
  • ['a', 'b', 'c', 'd'].copyWithin(0, 2, 4) → [ 'c', 'd', 'c', 'd' ]
• entries(): Iterable<[number, T]> 🔒
  • Returns an iterable over [index, element] pairs.
  • ES6
  • 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
  • [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
  • [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
  • [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
  • [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
  • [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
  • ['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
  • [0, 1, 2].includes(1) → true
  • [0, 1, 2].includes(5) → false
• indexOf(searchElement: T, fromIndex?: number): number 🔒
  • Return the index of the first element that is strictly equal to searchElement. Return -1 if there is no such element. Start searching at index fromIndex.
  • ES5
  • [0, 1, 2].indexOf(1) → 1
  • [0, 1, 2].indexOf(5) → -1
• 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”.