what is the prototype?

[runeveryday]

i want to learn javascript recently,now,there is one concepts i can't understand. which is the prototype, in javascript, there are two things about this. one is a framework. the other which is confused me a lot.

[trq]

I could, in one script create an object and give it some properties.

 

var foo = {
  a: 'blah'
}

 

I could then later add a method to the object...

 

foo.prototype.bar = function() {
  alert(this.a);
}

 

Its a method of inheritance.

[runeveryday]

I could, in one script create an object and give it some properties.

 

var foo = {
  a: 'blah'
}

 

I could then later add a method to the object...

 

foo.prototype.bar = function() {
  alert(this.a);
}

 

Its a method of inheritance.

 

want to  put your code in firebug,and make it can work, have some tries,but failed. i don't know how to  Instantiate  the anonymous  function.

 

 

 

[trq]

Actually, I'm thinking now that the 'prototype' property is only available on native objects.

[RichardRotterdam]

Try this:

// create foo constructor
var foo = function(a) {
// set property
this.a = a ;
}
// add bar function to foo
foo.prototype.bar = function() {
  alert(this.a);
}
// instantiate foo object
var instance = new foo('hello');
instance.bar();

[runeveryday]

Try this:

// create foo constructor
var foo = function(a) {
// set property
this.a = a ;
}
// add bar function to foo
foo.prototype.bar = function() {
  alert(this.a);
}
// instantiate foo object
var instance = new foo('hello');
instance.bar();

i am sorry,it doesn't show any result.

[runeveryday]

instance.bar();

what about this  line means?

[trq]

Indeed it does. You should get a pop-ups saying 'hello'.

 

I forgot it only works with objects literals. That's those instantiated using the 'new' keyword.

[trq]

instance.bar();

what about this  line means?

 

This line....

 

var instance = new foo('hello');

 

Creates an instance of the 'foo' object called 'instance'.

 

this line....

 

instance.bar();

 

then calls the bar() method of that object.

[runeveryday]

i am very glad about this. it's OK. many many thanks for your explaination.