The for...of function

The for loops over arrays in ES5 are often achieved using the for (index in array) syntax, which looks something like this:

var items = [1, 2, 3 ];
for (var index in items) {
var item = items[index];
…
 }

And ES6 adds the for...of syntax, which saves you a step, as you can see from the following code:

const items = [1, 2, 3 ];
for (const item of items) {
 …
 }