Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.javascript > #12846

Re: Adding new method to existing object

Show all headers | View raw

W dniu sobota, 17 marca 2012, 04:15:52 UTC+1 użytkownik Scott Sauyet napisał:
> CT wrote:
> > I want to extend my prototype object using another object. Just created some example code:
> >
> > http://jsfiddle.net/u9e7R/13/
> >
> > Can someone explain me how can I extend existing prototype object using new object?
> 
> David Mark pointed out the basic flaw in your code, that you munged
> the constructor.  I posted a fairly minimal fix to that earlier.  (I
> apologize for posting only a link; I know that's poor citizenship on
> USENET.  I was in a hurry, but that's no excuse.)  But that version is
> to me still fundamentally flawed.  It's far too complicated for what
> it does.  Below is another version with nearly the same behavior, but
> significantly simpler code.
> 
> There are two main differences in behavior: first, there is no factory
> function, just the plain constructor; and second, the addMethod
> function is attached to the constructor, not to the instances.  To me
> that simply makes sense, since it is updating the prototype.  If you
> meant this to apply to instances, the code would be far more simple.
> 
> Here is the simplified code, also available at <http://jsfiddle.net/
> u9e7R/18/>

It's simpler, like I've done this before, but not on the jsFiddle. Next I just wanted to return an instance of an object.

>     //~ I just attach this to the global namespace here instead
>     //~ of using the `global` variable to reference `this`.
> 
>     var JsCode = (function() {
>       var JsCode = function(params) {
>       };
> 
>       //~ Could use your technique of assigning the prototype,
>       //~ but I don't see the point.  I just refer to it directly.
>       var proto = JsCode.prototype;
> 
>       proto.test = function() {
>         console.log('Function test complete');
>         return this;
>       };
> 
>       //~ Since this is added to the prototype, there is no
>       //~ need for a function to find the prototype of the object.
>       JsCode.addMethod = function (name, fn) {
>         var old = proto[name];
> 
>         proto[name] = function() {
>           if ( fn.length == arguments.length ) {
>             return fn.apply( this, arguments );
>           } else if ( typeof old === "function" ) {
>             // really need error checking here.
>             return old.apply( this, arguments );
>           }
>         };
>       };
> 
>       return JsCode;
> 
>     })();
> 
>     var test2 = function() {
>       console.log('Function test2 complete');
>       return this;
>     };
> 
>     JsCode.addMethod('test2', test2);
> 
>     //~ Without the factory function, you must use `new`.
>     var jsc = new JsCode();
>     jsc.test2();  //~ or chain these as in the original
>     jsc.test();
> 
> 
> This does change the interface a little, but seems much cleaner.  If
> you really want a factory function, you could replace the `return`
> statement above with something like this:
> 
>     var result = function(params) {
>       return new JsCode(params);
>     }
>     result.addMethod = JsCode.addMethod;
>     return result;
> 
> (although that could be further simplified if desired.)
> 
> Does this capture the essence of what you're trying to do?

Yes! Thank You for clarifying me. This is exactly what I wanted to achieve.

-- 
Regards,
CT

Back to comp.lang.javascript | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-16 03:56 -0700
  Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-16 04:50 -0700
    Re: Adding new method to existing object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-03-16 15:31 +0100
      Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-16 11:51 -0700
        Re: Adding new method to existing object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-03-17 00:10 +0100
          Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-16 17:25 -0700
            Re: Adding new method to existing object Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-03-17 02:04 +0100
              Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-16 18:15 -0700
    Re: Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-16 10:18 -0700
      Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-16 11:56 -0700
      Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-16 13:01 -0700
        Re: Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-17 04:58 -0700
          Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-17 16:04 -0700
            Re: Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-18 04:24 -0700
              Re: Adding new method to existing object John G Harris <john@nospam.demon.co.uk> - 2012-03-18 13:16 +0000
  Re: Adding new method to existing object John G Harris <john@nospam.demon.co.uk> - 2012-03-16 17:09 +0000
    Re: Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-16 10:46 -0700
  Re: Adding new method to existing object Scott Sauyet <scott.sauyet@gmail.com> - 2012-03-16 13:43 -0700
  Re: Adding new method to existing object Scott Sauyet <scott.sauyet@gmail.com> - 2012-03-16 20:15 -0700
    Re: Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-17 05:17 -0700
    Re: Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-17 05:24 -0700
      Re: Adding new method to existing object David Mark <dmark.cinsoft@gmail.com> - 2012-03-17 16:16 -0700
        Re: Adding new method to existing object cezary.tomczyk@gmail.com - 2012-03-18 04:27 -0700

csiph-web