Comments on: How to do a non-destructive overwrite of a function in javascript

By: Stephan Wehner

Stephan Wehner — Mon, 02 Jun 2008 08:05:44 +0000

Couldn’t get this to work with “console.debug” (which comes with Firebug, for Firefox) — I got “too many recursions” with

var origcd = console.debug
console.debug = function(s) {
origcd(‘console-debug: ‘ + s)
}
:
:
:
console.debug(‘test’)

console.debug writes to a console, that can be viewed with Firebug.

Stephan

By: BK

BK — Tue, 22 May 2007 14:11:39 +0000

What do you mean by DOM Level 2?
Are you talking about the register event stuff?

By: James Craig

James Craig — Sat, 19 May 2007 20:31:24 +0000

Even without a library, try DOM Level 2 assignment and you won’t overwrite any of these DOM 1 assignments or other DOM 2 events.

By: Scott Becker

Scott Becker — Mon, 07 May 2007 20:07:30 +0000

Since you’re not really overwriting the function, but adding before and after callbacks, ActsAsAspect is an elegant way of doing this – http://beppu.lbox.org/articles/2006/09/06/actsasaspect

Basically, you can take a function or object or class with some existing methods:

MyObj.go = function() { alert(‘go’); }

and call actsAsAspect() on it like so:

actsAsAspect(MyObj);

then it gets some some extra methods – before, after, & around, which let you add listeners to that function like this:

MyObj.before(‘go’, function() { alert(‘do this before go() gets called!’) })

It’s short and sweet, I love that little script.

By: si

si — Fri, 04 May 2007 21:34:04 +0000

While I don’t like that method of event adding (I think a nice cross-browser addEvent function is far safer / nicer), it’s quite a pretty way of doing it – one good consequence is that you can specify whether yours happens before or after all of the existing methods.

Another similar “trick” which I like is overriding the alert() function to get rid of potentially missed debug code, like so:

_alert = alert;
alert = null;

By: Dan

Dan — Fri, 04 May 2007 14:14:11 +0000

@Boyan
I guess that a lot of librairies can take care of this… but sometimes you don’t have any librairie for a small web site or a bookmarklet…

Thanks for the correction…

By: Boyan

Boyan — Fri, 04 May 2007 13:38:29 +0000

Nice. Don’t most js libraries take care of this automatically already? Oh, and by the way (nitpick coming), the past tense of “stick” is “stuck” and not “stucked”

By: BK

BK — Thu, 03 May 2007 15:02:09 +0000

Here come the recuer again! Here Comes: THE CLOSURE!

function FnBuilder(){
var Old=document.getElementById(“myb”).onclick
function New(){Old();alert(5678);}
return New
}
document.getElementById(‘myb’).onclick=FnBuilder();
FnBuilder=null;