Using Objects in For Of Loops

Question

Why isn\'t is possible to use objects in for of loops? Or is this a browser bug? This code doesn\'t work in Chrome 42, saying undefined is not a function:

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Answer 1

It is possible to define an iterator over any giving object, this way you can put different logic for each object

var x = { a: 1, b: 2, c: 3 }
x[Symbol.iterator] = function* (){
    yield 1;
    yield 'foo';
    yield 'last'
}

Then just directly iterate x

for (let i in x){
    console.log(i);
}
//1
//foo
//last

It is possible to do the same thing on the Object.prototype object And have a general iterator for all objects

Object.prototype[Symbol.iterator] = function*() {
    for(let key of Object.keys(this)) {
         yield key 
    } 
 }

then iterate your object like this

var t = {a :'foo', b : 'bar'}
for(let i of t){
    console.log(t[i]);
}

Or this way

var it = t[Symbol.iterator](), p;
while(p = it.next().value){
    console.log(t[p])
}