JS: Array.from

(new in JS: ECMAScript 2015)

Array.from(xlist)

Convert xlist to array.

arg can be Array-Like Object or Iterable Object object.

If arg is Sparse Array, empty slots are treated as having value of undefined

// If arg is Sparse Array, empty slots are treated as having value of undefined

console.log(Array.from(Array(3)));
// [ undefined, undefined, undefined ]

// Convert Array-Like Object to Array
console.log(Array.from({ 0: "a", 1: "b", length: 2 }));
// [ "a", "b" ]

// Convert string to array of chars

console.log(
  JSON.stringify(Array.from("😃😄😅"))
);
// ["😃","😄","😅"]

Array.from(xlist, f)

Apply f to each.

The function f is passed 2 args:

1. current element
2. current index

console.log(
  Array.from("😃😄😅", (a, b) => [a, b]),
);
// [ [ "😃", 0 ], [ "😄", 1 ], [ "😅", 2 ] ]

Array.from(xlist, f, thisBinding)

• Use thisBinding as this (binding) in f.
• If thisBinding is not given, undefined is used.