Posted by Jochem Maas on 09/29/10 11:14

Richard Lynch wrote:
> On Tue, April 26, 2005 7:51 pm, Eli said:
>
>>I know this is not the forum, but I googled and couldn't find it, so
>>please try to help me with this.
>>
>>/*********/
>>function MyCls(name)
>>{
>> this.name=name;
>>}
>>function SayHi()
>>{
>> alert('Hi, '+this.name+'!');
>>}
>>var obj=new MyCls('PHP');
>>obj.name='JavaScript'; //this will call SayHi() function
>>/*********/
>>
>>I have a class in JS with a property variable in it. How can I execute a
>>function when the property value is changed?
>
>
> I don't think JavaScript has any way to hook into a property being changed
> and take some action on that...
>
> It *MIGHT* have 'private' properties, that can't be changed by child
> classes, and then you'd have to use a function to change the property, and
> then your function that changes the property can do whatever it wants...
>
> But that all assumes JavaScript even has "private" properties, which it
> may not have.

...it has closures - which allow you to create/emulate private properties as you
know them from other langs, I abuse this occasionally but I hardly understand it.
(so what Richard described can be done in JS)

a couple of points about JavaScript:
1. everything is a object!
2. the object model is prototype based, which is quite orthoganol to PHP's object
model (for instance) - something that is liable to bite you in the ass a few times.
3. is a _lot_ more powerful (and well thought out) than its given credit for.
4. in terms of being a 'dynamic' language it makes PHP look like its statically typed
& compiled ;-) - which is in no way a dig at PHP (which is lovely just the way it is :-)

nice one Marek for the heads up on the watch() method, much obliged to you!
here is a link that explains the watch method for those too lazy to google:
http://www.devguru.com/Technologies/ecmascript/quickref/watch.html

now lets get back to PHP on this list shall we ;-)

>
> Your only other option is to just DOCUMENT that nobody should ever alter
> ".name" directly, but should always use your changeName() function which
> does whatever you want it to do.
>

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