Question

Possible Duplicate:
Use of 'prototype' vs. 'this' in Javascript?

I am confused with these two type of adding a method to a function. Let me explain with an example.

var foo = function(){
    this.bar = function(){alert('I am a method')}
}

foo.prototype.baz = function(){alert('I am another method')}

var car = new foo();

Now at this point we can use baz and bar methods for car. Well, but what is the difference between them. What is the nuance adding a method to function’s prototype or it’s constructor.

Thanks..

Answer 1

Functions assigned to the prototype will be shared by all instances; functions assigned in the constructor will have a separate function object per instance.

Also, functions assign in the constructor can use the constructor’s variables and parameters.

For example:

var foo = function(param){
    this.bar = function() { alert('I can see a parameter: ' + param); };
}

foo.prototype.baz = function() { alert('I can't see foo's parameters'); };

var car = new foo("Hi there!");
car.bar();