How to list the properties of a JavaScript object?

Question

Say I create an object thus:

var myObject =         {"ircEvent": "PRIVMSG", "method": "newURI", "regex": "^http://.*"}; 

What is the best way to retrieve a list of the property names? i.e. I would like to end up with some variable 'keys' such that:

keys == ["ircEvent", "method", "regex"] 

Answer 1

In modern browsers (IE9+, FF4+, Chrome5+, Opera12+, Safari5+) you can use the built in Object.keys method:

var keys = Object.keys(myObject); 

The above has a full polyfill but a simplified version is:

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

Alternatively replace var getKeys with Object.prototype.keys to allow you to call .keys() on any object. Extending the prototype has some side effects and I wouldn't recommend doing it.