Access nested JavaScript object value from string key

byString.js

 /**
  * Access nested JavaScript object value from string key
  *
  * @memberof Object.prototype
  * @param s {String} property string
  * @return {String} value for property string
  *
  * [http://stackoverflow.com/questions/6491463/accessing-nested-javascript-objects-with-string-key]
  */
Object.prototype.byString = function(s) {
	s = s.replace(/\[(\w+)\]/, ".$1");
	s = s.replace(/^\./, "");
	var self = this,
	    a = s.split(".");
	for (var i = 0; i < a.length; i++) {
		var k = a[i];
		if (k in self) {
			self = self[k]; 
		} else  {
			return;
		}
	}
	return self;
}