How to write a function instead of using the built in Object.keys() method?

Question

How would I write the code below as function and not using the built in Object.keys() method? Thank you!

var obj = { Name: 'Joe', Age: 18, pass: true };
console.log(Object.keys(obj)); // =>  [ 'Name', 'Age', 'pass' ]

See polyfill [here](https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Reference/Global_Objects/Object/keys) — Anson, Feb 18 '17 at 07:54

Shayan · Accepted Answer · 2017-02-18T08:13:27.463

2

Do you mean this?

function getKeys(obj){
  return Object.keys(obj)
}

or

function getKeys(){
    var keys = [];
    for (var key in foo) {
        keys.push(key);
    }
    return keys;
}

or you can do

Object.prototype.getKeys = function(o, f, ctx) {
    return Object.keys(o);
}
// obj.getKeys() => [ 'Name', 'Age', 'pass' ]

edited Feb 18 '17 at 08:13

answered Feb 18 '17 at 07:46

Shayan

Is it possible to write as a function without using the Object.keys in the code at all? – learninghowtocode Feb 18 '17 at 07:48
@learninghowtocode you mean you want something like `obj.getKeys()` ?? – Shayan Feb 18 '17 at 07:49
why are you so against Object.keys? – A. L Feb 18 '17 at 07:50
The third one doesn't allow for `obj.getKeys()`. You would have to set the function to `Object.prototype.getKeys` – 4castle Feb 18 '17 at 07:55
@4castle are you sure?? i use it in an application, and it's work. let me check, thanks for mention – Shayan Feb 18 '17 at 07:56
LOL! I'm not against Object Keys I'm just not supposed to use them to learn at the moment. :) Thanks @Shayan your second response was what I was looking for. Thanks for everyone's help!! Much appreciated! – learninghowtocode Feb 18 '17 at 07:57
you miss [`Object#hasOwnProperty`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty) check for an equvalent of [`Object.keys`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys) and some newer checks for it. – Nina Scholz Feb 18 '17 at 08:57

score 0 · Answer 2 · answered Feb 18 '17 at 08:01

0

@Shayan's response here is what I was looking for:

function getKeys(){
    var keys = [];
    for (var key in foo) {
    keys.push(key);
    }
    return keys;
 }

answered Feb 18 '17 at 08:01

learninghowtocode

Rather than post a duplicate answer, you can click the check mark beside an answer if it solved your problem. – 4castle Feb 18 '17 at 08:02
Thanks for the helpful tip! – learninghowtocode Feb 18 '17 at 08:13

2 Answers2