JS: Array.prototype.filter

• myArray.filter (f)
• myArray.filter (f, thisArg)

Return a new array, with elements that f return true.

Original array is not changed.

If thisArg is given, it will be used as this value of f. If it is not given, undefined is used.

[see JS: “this” Binding]

f is called with 3 arguments: the value of the element, the index of the element, and the object being traversed.

const isEven = ((x) => ( x % 2 === 0 ) )

const arr = [7,3,4,2];

console.log( arr.filter ( isEven ) ); // [ 4, 2 ]

// original not changed
console.log( arr ); // [ 7, 3, 4, 2 ]

Reference

ECMAScript® 2016 Language Specification#sec-array.prototype.filter