JavaScript: Array vs. Objects

Regular Array	Object/Associate Array
// regular array (add an optional integer argument to control array's size) var myCars=new Array(); myCars[0]="Saab"; myCars[1]="Volvo"; myCars[2]="BMW";	//Create a direct instance of an object personObj=new Object(); personObj.firstname="John"; personObj.lastname="Doe"; personObj.age=50; personObj.eyecolor="blue";
// create literal array var myCars=["Saab","Volvo","BMW"];	//create alternative syntax (using object literals):  personObj = {firstname:"John", lastname:"Doe", age:50, eyecolor:"blue"};
// find total length of array document.write(myCars.length); // output: 3	Object.size = function(obj) {    var size = 0, key;    for (key in obj) {      if (obj.hasOwnProperty(key)) size++;    }     return size; }; document.write(Object.size(personObj)); // output: 4
// print individual element of array document.write(myCars[0]); // output: Saab	document.write(personObj['firstname']); // output: John document.write(personObj.firstname); // output: John
// print all elements of array for(var x = 0; x < myCars.length; x++){      document.write(myCars[x] + " "); } // output: Saab Volvo BMW	var x; for (x in personObj) {      document.write(personObj[x] + " "); } // output: John Doe 50 blue

Refer site:
http://www.w3schools.com/js/js_obj_array.asp
http://www.w3schools.com/js/js_objects.asp