Object-Oriented JavaScript

Advanced Web Applications With Object-Oriented JavaScript @ MSDN

In JavaScript, objects are just collections of name/value pairs
—think of a JavaScript object as a dictionary with string keys

var userObject = new Object();
userObject.lastLoginTime = new Date();
alert(userObject.lastLoginTime);

does exactly the same thing as this:

var userObject = {}; // equivalent to new Object()
userObject["lastLoginTime"] = new Date();
alert(userObject["lastLoginTime"]);

We can also define the lastLoginTime property directly within userObject’s definition like this:

var userObject = { "lastLoginTime": new Date() };
alert(userObject.lastLoginTime);