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

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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]

> 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);

`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.

The original event object is available with the `originalEvent' property
of the object referred to by `e2'.

AISB, the proprietary event handler properties should be avoided.


PointedEars
-- 
Prototype.js was written by people who don't know javascript for people
who don't know javascript. People who don't know javascript are not
the best source of advice on designing systems that use javascript.
  -- Richard Cornford, cljs, <f806at$ail$1$8300dec7@news.demon.co.uk>

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<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

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