prototype in javascript

Question

Javascript functions can also be declared prototype like

<object name>.prototype.<variable name>=function(){
//
//
}

How it is different than following declaration

<object name>.<variable name>=function(){
//
//
}

How prototype functions different than normal functions in javascript ?

Answer 1

functions declared on a base object's prototype are inherited by all instances of that object type.

For example..

String.prototype.foo = function () {
  return 'bar';
};

Now, every string will have the function foo() available.

'test'.foo(); // returns 'bar'

Read more about prototype-based inheritance here

Answer 2

It's an OO javascript package that has great built in AJAX functions that utilize the XmlHttpRequest function, DOM manipulation, and JSON data transfer.

The full API documentation is here.

Answer 3

Prototype functions are instance functions, whilst normal functions are "static" functions. Functions declared on class's prototype will available on all instances of that class.

var MyClass = function(){
};
MyClass.staticFunction = function(){alert("static");};
MyClass.prototype.protoFunction = function(){alert("instance");};

MyClass.staticFunction(); //OK
MyClass.protoFunction (); //not OK

var myInstance = new MyClass ();
myInstance.staticFunction(); //not OK
myInstance.protoFunction (); //OK

Answer 4

Matt and Igor have already provided enough code samples, but one of the best articles (short, correct and to the point) that you can read is Prototypal Inheritance, by Douglas Crockford.

There are also lots of different ways to facilitate inheritance through popular libraries (Dojo, Prototype, etc)