what is "function" here means ?

[Nakata kokuyo]

hi, good day ,

can expert here explain what is "function" means here?

 
self.AJAX.onreadystatechange = function( ) {
        //logger("AJAXRequest Handler: State =  " + self.AJAX.readyState);
        self.process(self.AJAX);
    }
 

how to use it ? and when should we use it ?

can someone give better example ?

thank you for guidance

[Bear Bibeault]

Functions are 1st-class objects in Javascript and as such can be declared as literals. The syntax you are seeing here is creating a function literal and assigning it to the onreadystate property of an object.

This construct is also sometimes termed a "closure".
[ August 02, 2006: Message edited by: Bear Bibeault ]

[Nakata kokuyo]

bear, i still can't understand it ? do you mind to give me better example?

[Eric Pascarello]

Basic example of extending objects with prototype:

var message = new Object;
 
message.informUser = function(){
  this.text = null;
}
 
message.informUser.prototype.tell = function(){
  if(this.text == null)alert("The programmer screwed up");
  else alert(this.text);
}
 
var message1 = new message.informUser();
message1.text = "Hello world";
message1.tell();
 
var message2 = new message.informUser();
message2.text = "foo";
message2.tell();
 

Eric

[Nakata kokuyo]

great , eric .. thanks for useful sample ,

meaning i can assume it as class in java ? something like following for this sample

message.informUser = function(){ this.text = null;}

as following prototype ?

class message.informUser ()
{
   this.text = null 
}

[Bear Bibeault]

Not really.

Take the following example:

someObject.someProperty = function() { alert('hi!'); }
    

this is similar to:

function hiThere() { alert('hi!'); }
 
someObject.someProperty = hiThere;
    

In the first example no separate, named function is created -- an unnamed function is created using a function literal. In the second, a reference to a named function is stored.

In either example, a reference to a function that says "hi!" is stored int he someProperty property of someObject.

(There is a difference between the 2 examples regarding how variables are scoped, but that's a nuance that might just be confusing at this point).

[Nakata kokuyo]

thanks for guidance , bear , i'm understand it better now