Question

Let’s say I have this part.

<input id="text1" type="text" name="text1" onchange="alert('valueA');" /><br />
<input id="text2" type="text" name="text2" /><br />

What I’d want to do is to get the onchange event handler of the input=”text1″ and attach to another element’s event, “text2”.
So far , it’s okay.I can get DOM0 hanlder of input “text1” and attach to text 2 as DOM2 .

_handler= $('#text1')[0].onchange;
            $('#text2').change(function (event) { 
            if (typeof _handler=== "function") {
                        _handler.call(this, event); 
            }

But, the problem is , I want to change/add some js codes before attaching into “text2”.
For example , before attaching into “text2”, I want to change “alert(‘valueA’);” into “alert(‘valueA.This is text2’)”;
How can I do to achieve this?
The alert statement is just the example ,and please don’t give solutions something like storing alert message into global variable, show the variable’s value..etc.

Thanks.

Answer 1

This cannot be done. You cannot change the code inside of a function.

Although Javascript functions are mutable objects, you can only add properties and methods to them, but you can’t change the code inside of ’em.

---

If you want to use the evil eval (as you’ve specified in the comments), you could convert the function to a string, replace whatever text you want inside the function, and then eval it:

$('#text2').change(function (event) { 
    eval(
        '(' + $('#text1')[0].onchange.toString().replace('valueA', 'valueB') + ')()'
    );
});

And here’s the fiddle: http://jsfiddle.net/A4w2W/

But, please please please don’t do this. This is the worst possible way to write code, ever!!
You should seriously reconsider your approach to this whole matter.