The for-of loop in ES6

The for-of loop is new in ES6:

 for (let x of iterable) {
   ···
 }

The loop iterates over iterable and assigns each of the enumerated items to the iteration variable x. let keeps the scope of x to within the loop.

You can convert data structures into iterable objects using the entries(), keys() and values() methods:

// entries() returns a [key,value] array
let a = ['E', 'n', 'k', 'i'];
for (let pair of a.entries()) {
  console.log(pair);
}
// [0, 'E']
// [1, 'n']
// [2, 'k']
// [3, 'i']

Note: you can use this loop on strings, but it loops over Unicode code points which may be represented by more than one character.