How Can I Efficiently Get a List of JavaScript Object Property Names?

Listing Properties of JavaScript Objects

When working with JavaScript objects, retrieving a list of property names can be essential. Suppose you have an object defined as follows:

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

The question arises: how can we efficiently obtain a list of the property names (e.g., ["ircEvent", "method", "regex"])?

Modern Browsers:

In modern browsers, the built-in Object.keys method provides an elegant solution:

var keys = Object.keys(myObject);

Polyfill for Legacy Browsers:

For browsers lacking native support, a simplified polyfill can be implemented:

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

An alternative approach involves extending the Object prototype:

Object.prototype.keys = function() {
   var keys = [];
   for (var key in this) {
      keys.push(key);
   }
   return keys;
};

This method allows you to call .keys() on any object. However, extending the prototype may have side effects and is generally not recommended.

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