JavaScript Array Methods
ES6
Static Array methods
Array.from()
const arr2 = Array.from(arguments) // ES6
If a value is iterable (as all Array-like DOM data structure are by now), you can also use the spread operator (…) to convert it to an Array:
const arr1 = [..."abc"]
// ['a', 'b', 'c']
const arr2 = [...new Set().add("a").add("b")]
// ['a', 'b']
Array.of()
This returns an array of the passed parameters
console.log(Array.of(1, 2, 3, 4)) // [1, 2, 3, 4]
Array.prototype methods
Array.prototype.fill()
const arr2 = new Array(2).fill(undefined)
// [undefined, undefined]
Array.prototype.copyWithin()
The method signature is:
Array.prototype.copyWithin(target : number,
start : number, end = this.length) : This
It copies the elements whose indices are in the range [start,end) to index target and subsequent indices. If the two index ranges overlap, care is taken that all source elements are copied before they are overwritten. I am confused as to how this is in any way useful.
const arr = [0, 1, 2, 3]
console.log(arr.copyWithin(2, 0, 2)) // [0, 1, 0, 1]
Searching for elements
Array.prototype.findIndex()
console.log([6, -6, 8].findIndex((x) => x < 0)) // 1
Array.prototype.find()
console.log([6, -6, 8].find((x) => x < 0)) // -6
Iteration
Array.prototype.entries()
console.log(Array.from(["a", "b"].entries())) // [ [ 0, 'a' ], [ 1, 'b' ] ]
Array.prototype.values()
console.log(Array.from(["a", "b"].values())) // ['a', 'b']
Array.prototype.keys()
console.log(Array.from(["a", "b"].keys())) // [0, 1]
ES2016
Array.prototype.includes()
Tells you if array includes a certain element:
console.log(["a", "b", "c"].includes("a")) // true
console.log(["a", "b", "c"].includes("d")) // false