iterator.example.js

function iteratorFactory(obj) {
    var nextIndex = 0;
    var keys = Object.keys(obj);
    var end = keys.length;
    var next = function(){
       return nextIndex < end ? { value: { [keys[nextIndex]]: obj[keys[nextIndex++]]}, done: false } : { value: undefined, done: true }
    }
    return { next: next };
}

let ob = { age: 41, name: 'Leonard', profession: 'JavaScript Developer' };
let obit = iteratorFactory(ob);
obit.next(); // returns { value: { age: 41 }, done: false }
obit.next(); // returns { value: { name: 'Leonard'}, done: false }
obit.next(); // returns { value: { profession: 'JavaScript Developer'}, done: false }
obit.next(); // returns { value: undefined, done: true }