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

Groups > comp.lang.javascript > #8648

Re: <ul><li><ul><li>... onclick() only for one node ?

Show all headers | View raw

On 25/11/2011 17:28, Thomas 'PointedEars' Lahn wrote:
> Jukka K. Korpela wrote:
>
>> 2011-11-25 17:10, Jörg Weule wrote:
>>> at<ul><li><ul><li>...</li></ul></li></ul>  I got the click event on the
>>> whole tree and want to process the event for only on one node.
>>
>> Applying the techniques explained at
>> http://www.quirksmode.org/js/events_order.html
>> you could write
>>
>> var l = document.createElement("li");
>> l.onclick = handler;
>> function handler(e)
>> {
>> if (!e) var e = window.event;
>
> That `VariableDeclaration' is pointless; it also reduces runtime efficiency
> slightly.  The Variable Object (or the Variable Environment) already had the
> variable `e' instantiated per the function's argument list, so the
> VariableDeclaration has no effect (other than checking for a previous
> binding, which is what reduces runtime efficiency).  [ES 5.1, section 10.5]
>

ACK as to 'VariableDeclaration is pointless', although that reduction in 
runtime efficiency, if noticeable / measurable, should be dependent on 
the actual JavaScript Engine in use.

>> e.cancelBubble = true;
>> if (e.stopPropagation) e.stopPropagation();
>> // do the real handling here
>> }
>
> One should *either* attempt to set the `cancelBubble' property to `true'
> *or* attempt to call the stopPropagation() method, depending on what is the
> result of a feature test, because `e' refers to a host object and should not
> be accidentally augmented.  To that end, jsx.dom.createEventListener()
> solves this with
>
>      e2.stopPropagation = (function(e) {
>        if (jsx_object.isMethod(e, "stopPropagation"))
>        {
>          return function() {
>            e.stopPropagation();
>          };
>        }
>
>        if (typeof e.cancelBubble != "undefined")
>        {
>          return function() {
>            e.cancelBubble = true;
>          };
>        }
>      })(e);
>

"Either cancelBubble property or stopPropagation() method" means only 
one check is necessary, not both, as there is not a 3rd option. So:

   e2.cancelPropagation = function (e) {
     e = e || window.event;
     if (typeof e.stopPropagation !== 'undefined') { // W3C standard
       e.stopPropagation();
     } else { e.cancelBubble = true; } // IE
   };


> `e2' is a reference to a native user-defined object that is passed in place
> of the event host object (referred to by `e') to the wrapped event listener
> then (revision 233, line 459):
>
>    return f.call(this, e2);
>
> Which allows to call e.stopPropagation() in the wrapped listener (f)
> regardless which DOM implementation is supported.
>
> A similar wrapper method exists for the preventDefault() method.  But it
> turns out that the `returnValue' property, which is the proprietary
> replacement for the preventDefault() method, cannot be feature-tested.
> So `returnValue' is used if preventDefault() is unavailable regardless.
>
   someObj.cancelDefault = function (e) {
     e = e || window.event;
     if (typeof e.preventDefault !== 'undefined') { // W3C standard
       e.preventDefault();
     } else { e.returnValue = false; } // IE
   };

<snip>


-- 
Joao Rodrigues (J.R.)

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

Thread

<ul><li><ul><li>... onclick() only for one node ? Jörg Weule <weule@7b5.de> - 2011-11-25 16:10 +0100
  Re: <ul><li><ul><li>... onclick() only for one node ? Arno Welzel <usenet@arnowelzel.de> - 2011-11-25 17:30 +0100
  Re: <ul><li><ul><li>... onclick() only for one node ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-11-25 17:58 +0100
    Re: <ul><li><ul><li>... onclick() only for one node ? Jörg Weule <weule@7b5.de> - 2011-11-25 18:42 +0100
      Re: <ul><li><ul><li>... onclick() only for one node ? Martin Honnen <mahotrash@yahoo.de> - 2011-11-25 19:11 +0100
        Re: <ul><li><ul><li>... onclick() only for one node ? Jörg Weule <weule@7b5.de> - 2011-11-25 19:37 +0100
        Re: <ul><li><ul><li>... onclick() only for one node ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-11-25 20:04 +0100
  Re: <ul><li><ul><li>... onclick() only for one node ? "Jukka K. Korpela" <jkorpela@cs.tut.fi> - 2011-11-25 20:27 +0200
    Re: <ul><li><ul><li>... onclick() only for one node ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-11-25 20:28 +0100
      Re: <ul><li><ul><li>... onclick() only for one node ? "J.R." <groups_jr-1@yahoo.com.br> - 2011-11-25 21:57 -0200
        Re: <ul><li><ul><li>... onclick() only for one node ? "Jukka K. Korpela" <jkorpela@cs.tut.fi> - 2011-11-26 09:14 +0200
          Re: <ul><li><ul><li>... onclick() only for one node ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-11-26 12:53 +0100
        Re: <ul><li><ul><li>... onclick() only for one node ? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2011-11-26 12:51 +0100

csiph-web