Difference between creating object using prototype and object literal notation

var MyClass={
   init:function(){

   }
}

defines an object called MyClass with a member function init. This is object literal notation. There is only single instance of this object; you can't create a new one. You can only say for example

MyClass.init();

you can't say

var foo = new MyClass(); (this will cause an error)

On the other hand,

var Myclass=function(){};
Myclass.prototype.init=function(){}

is different; it defines a "class" (or constructor function as it can be called) which has a function init but which you can create multiple instances of; each instance will have the init() function.

var foo = new Myclass();
var bar = new Myclass();
foo.init();
bar.init();

So which you use really depends on what you need it for; if you're making an object that has some utility functions or maybe represents a service which only needs a single copy ever, the first is fine; whereas if you need to be able to make multiple instances because each instance's data might need to change indepdendently, use the second.