function Pe(){};

var len = 1000000;
var half = len / 2;
var array = [];
var last = new Pe();
while(len--) {
	array.push(new Pe());
}
array.push(last);

(function(){
	var d = new Date().getTime();
	var i = array.indexOf(last);
	console.log('(indexOf)  Index: ' + i + '\tmilliseconds: ' + (new Date().getTime() - d));
})();

(function(){
	var d = new Date().getTime();
	var index = -1;
	for(var i = 0, len = array.length; i < len; i++) {
		if(array[i] === last) {
			index = i;
			break;
		}
	}
	console.log('(for loop) Index: ' + index + '\tmilliseconds: ' + (new Date().getTime() - d));
})();