Array Of & Array From

ES6 added a few static array methods which can come in handy. Array.of creates a new array from any number of arguments and no matter the type of the arguments:

const argString = Array.of('foobar');
> ["foobar"]

const argNums = Array.of(7,8);
> [7, 8]

const argObj = Array.of({foo: 'bar'}, { bar: 'foo' }, [0]);
> [{foo: 'bar'}, { bar: 'foo' }, [0]]

Array.from lets you create an array from array like objects, which means objects with a length property and indexed elements, or iterable objects (Map, Set). Array.from accepts as a second argument a map function that can operate over every item in the array and it also takes a third argument which can be used as the this scope when executing the map function.

const stringHasLengthCreatesArray = Array.from('willBeArray');
> ["w", "i", "l", "l", "B", "e", "A", "r", "r", "a", "y"]

const notArrayLikeNum = Array.from(123);
> []

const notArrayLikeOb = Array.from({foo: 'bar'});
> []

const multiples = Array.from([1, 2, 3], x => x * x);
> [1, 4, 9]