add a function to an event

[pitchoo]

I use this code to add a function for the onchange event:

obj.onchange = function () { calculateExpr(expression,fieldType) }

but how can I add this function without deleting the preceding functions defined in this event?
I tried with += but it doesn't work...

Thanks

[whackaxe]

if your funtions dont return anything then oyu could try this

function changeevent()
{
//first function you want to put in
[etc...]

//second function you wanted to put in
[etc...]

//third function you wanted to put in
[etc...]
}

obj.onchange = changeevent()

[pitchoo]

It should be something like this:


obj.onchange = function () { obj.onchange ;calculateExpr(expression,fieldType) }


but how can obj.onchange be interpreted as the content of hum ..."obj.onchange"? Is it clear?

[whackaxe]

sorry i dont follow what you mean

but how can obj.onchange be interpreted as the content of hum ..."obj.onchange"? Is it clear?

[pitchoo]

I'll try to be clearer:

I have an object which is composed of an onchange event.
This event is composed of function A.

Now I need to add dynamically a second function to the object's onchange event: function B.

So I do this:

obj.onchange = function() {functionB;};

But in this case function A is logically deleted, so my question is how can I add function B and keep function A in the event?

[jkd]

obj.addEventListener('change', myListener, false);
// for Gecko (NS6, NS7, Mozilla, Beonex, K-meleon, and Galeon), and other DOM2 browsers

obj.attachEvent('onchange', myListener);
// for IE

There is one way, or you could try:

obj.oldOnchange = obj.onchange;
obj.onchange = function() {
//my normal code
obj.oldOnchange();
}

[pitchoo]

I have a last question about the 2 methods: addEventListener and attachEvent, which one corresponds to a JavaScript standard? Is it IE's method or Gecko's method?

[pitchoo]

http://webfx.nu/dhtml/ieemu/eventlisteners.html

[jkd]

Gecko's method of course - addEventListener is defined in the DOM2 Events specs.

document.implementation.hasFeature('Events','2.0')

is true in Gecko, false in IE. :)