var myObject = {
    a: 2,
    b: 3
}
Object.defineProperty(myObject, Symbol.iterator, {
    enumerable: false,
    writable: false,
    configurable: true,
    value: function () {
        var o = this;
        var idx = 0;
        var ks = Object.keys(o)
        return {
            next: function () {
                return {
                    value: o[ks[idx++]],
                    done: (idx > ks.length)
                };
            }
        }
    }
})
var it = myObject[Symbol.iterator]();
it.next()
it.next() 
it.next() 
it.next() 
for (var item of myObject) {
    console.log(item)
}
/*version2*/
var myObject = {
    a: 2,
    b: 3,
    [Symbol.iterator]: function () {
        var o = this;
        var idx = 0;
        var ks = Object.keys(o)
        return {
            next: function () {
                return {
                    value: o[ks[idx++]],
                    done: (idx > ks.length)
                };
            }
        }
    }
}
for (var item of myObject) {
    console.log(item)
}