how to write userdefined callback function

[newlearner]

Hi,
i know we can wirte a userdefined callback function..

I had a try for a long time though i feel im near but not able to coin out the exact thing. can any body tell me about a user defined callback function... and a sample on how to write it...


looking forward for a reply..


Thanks in advance for your reply...

[pbmods]

Heya, New Learner.

You may find this article useful.

[newlearner]

Heya, New Learner.

You may find this article useful.

thx pbmods... The article was useful...

but my doubt is..

whenever http.onreadystatechange value is changed the assigned function is called...

similarly.. i need to create a userdefined handler for ex:
x = somefunction
like onreadystatechange(which is a browser object) whenever the value of x is changed thn somefunction should be initiated.

Is this Possible..


looking forward for a reply..

Thanks in advance

[gits]

hi ...

so x is a simple js-variable and you want to react with 'somefunction' when the value of x changes?

but i assume you already know WHERE x changes (in case its your own code)? ... everytime a value is assigned to x you may call 'somefunction' or use a set-function for x instead of a simple assignment ... and in that so called 'setter' you may call whatever you want ...

hope i didn't misunderstood your problem?

another method would be to define a watcher:

obj.watch(property, callback);
 

and to detach the watcher:

obj.unwatch(property);
 

kind regards

[newlearner]

hi ...

so x is a simple js-variable and you want to react with 'somefunction' when the value of x changes?

but i assume you already know WHERE x changes (in case its your own code)? ... everytime a value is assigned to x you may call 'somefunction' or use a set-function for x instead of a simple assignment ... and in that so called 'setter' you may call whatever you want ...

hope i didn't misunderstood your problem?

another method would be to define a watcher:

obj.watch(property, callback);
 

and to detach the watcher:

obj.unwatch(property);
 

kind regards

tnx for the idea...
I have tried out the way u suggested ... it works fine...

But my doubt is...
we write:

http.onreadystatechange=response;

response is triggered whenever onreadystatechange is chnged from 0 .. 4.

similarly... i write

function base() {
  this.x=0;
}
 
base = new base()
 
function tst(){
  base.x = callfun;
}

in a html page i have 2 buttons

on a 1st onclick event i say base.x=1// I need callfun to be triggered (coz x has changed)
on a 2nd onclick event i say base.x=2// I need callfun to be triggered (coz x has changed)

Is This possible...?


Looking for ward fir a reply..

Thanks in advance

[acoder]

Please use CODE tags when posting code, e.g.
[code=javascript]Javascript code goes here[/code.] (remove the dot).

[gits]

hi ...

have a look at the following example:

<script>
function OBJ() {
    this.x = 0;
}
 
OBJ.prototype.increment_val = function() {
    this.x++;
}
 
var obj = new OBJ;
 
obj.watch('x', function(val, oldval, newval) {alert(newval); return newval;});
</script>
 
<a href="#" onclick="obj.increment_val();">increase obj counter</a>
 

kind regards

ps: note watch will not work with IE ... so the 'setter'-method is probably to be preferred :)