Iterators and iterables

ES6 introduces a new mechanism of iterating over data. Traversing a list of data and doing something with it is a very common operation. ES6 enhances the iteration constructs. There are two primary concepts involved with this change-iterators and iterables.

Iterators

A JavaScript iterator is an object that exposes the next() method. This method returns the next item from the collection in the form of an object that has two properties-done and value. In the following example, we will return an iterator from an array by exposing the next() method:

    //Take an array and return an iterator 
    function iter(array){ 
      var nextId= 0; 
      return { 
        next: function() { 
          if(nextId < array.length) { 
            return {value: array[nextId++], done: false}; 
          } else { 
            return {done: true}; 
          } 
        } 
      } 
    } 
    var it = iter(['Hello', 'Iterators...