What is the use case for Javascript's (ES6) Array.of()?

Question

I came across the new Array.of() method that\'s been finalized in ES6, and I was wondering when one might use:

var a = Array.of(\'foo\', \'bar\');
         


        

Answer 1

I googled it for you, and the first result had a great example:

Array.of(...items)

If you want to turn several values into an array, you should always use an array literal, especially since the array constructor doesn’t work properly if there is a single value that is a number (more information on this quirk):

new Array(3, 11, 8)
// => [ 3, 11, 8 ]
new Array(3)
// => [ , ,  ,]
new Array(3.1)
// => RangeError: Invalid array length

But how are you supposed to turn values into an instance of a sub-constructor of Array then? This is where Array.of() helps (remember that sub-constructors of Array inherit all of Array’s methods, including of()).

class MyArray extends Array {
    ...
}
console.log(MyArray.of(3, 11, 8) instanceof MyArray); // true
console.log(MyArray.of(3).length === 1); // true

It's also worth noting that Array.of() also preserves Array's API compatibility with TypedArray. With TypedArray (Int32Array, UInt32Array, etc.), of() is very useful. From MDN:

Uint8Array.of(1);            // Uint8Array [ 1 ]
Int8Array.of("1", "2", "3"); // Int8Array [ 1, 2, 3 ]
Float32Array.of(1, 2, 3);    // Float32Array [ 1, 2, 3 ]
Int16Array.of(undefined);    // IntArray [ 0 ]