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

Because object literal does not have the Symbol.iterator property. To be specific, you can only iterate over String, Array, Map, Set, arguments, NodeList(not widely support) and Generator with for...of loop.

To deal with Object Literal iteration, you have two options.

for...in

for(let key in obj){
    console.log(obj[key]); 
}

Object.keys + forEach

Object.keys(obj).forEach(function(key){
    console.log(obj[key]);
});

Answer 2

I made objects iterable with this code:

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

Usage:

for(let [ key, value ] of {}) { }

Alternativly:

for(let [ key, value ] of Object.entries({})) { }