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

Groups > comp.lang.javascript > #27367

Re: XMLHttpRequest and Google Chrome

Show all headers | View raw

Christoph M. Becker wrote:

> The onload property of the window element

s/element/object/

> is supposed to hold the reference to a Function object (or null).  This 
> function object is automatically called (with a single argument, namely 
> the respective Event object[1]) after the documented has been loaded.

s/documented/document/

Also, one must carefully consider what it means that “a document has been 
loaded”.  Historically, there has been an inconsistency among layout engines 
with regard to loading the image resources referred by a document, for 
example.

> […]
> [1] This argument isn't supplied in old versions of MSHTML.

… and in MSHTML 9+ when in a backwards-compatible browser mode.

In general, one should not write such code, but use a wrapper that only 
falls back to “.on…” in case .addEventListener() is not available, in a way 
that works like .addEventListener().

The disadvantage of the .on…  properties is that, if used directly, the code 
not only overwrites any event listener previously defined in *this* way, but 
today’s test in WebKit as of "Mozilla/5.0 (X11; Linux x86_64) 
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36" 
shows that this can place the new event listener *after* all other listeners 
for the same event type.

This can be tested by example of the “click” event of the “body” element 
using

  document.body.onclick = function () { console.log(1337); };

  document.body.addEventListener("click",
    function () { console.log(42); }, 
    false);

  document.body.onclick = function () { console.log(23); };

and then clicking somewhere within the document body.  In the aforementioned 
environment, I get

  42
  23

which shows that the event listener is replaced *and* moved.

After a subsequent

  document.body.addEventListener("click",
    function () { console.log(1701); }, 
    false);

call, I get

  42
  23
  1701

when clicking, which shows that .addEventListener() preserves the listener 
order: the new listener comes not only after all listeners added with 
.addEventListener(), but all listeners for the same event no matter how they 
were added (including .onclick assignments).

If I repeat the second .onclick assignment, I get

  42
  1701
  23

when clicking.  So I must assume that this is the implemented behavior and 
cannot be attributed to an arbitrary order of calling the listeners.

[I have not checked the HTML5 Specification for this yet.  That 
.addEventListener() would preserve listener order was specified in DOM Level 
3 Events, and implemented so before HTML5, but that specification did not 
say anything about how .addEventListener() was supposed to work in 
combination with event-handler properties on element objects.]

That said, such considerations may not be relevant with certain other 
objects and event types.  It is then merely a matter of consistency in the 
application design.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
Please do not cc me. / Bitte keine Kopien per E-Mail.

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

Thread

XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-12 19:36 +0100
  Re: XMLHttpRequest and Google Chrome JJ <jj4public@vfemail.net> - 2015-04-13 12:33 +0700
    Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 07:41 +0100
  Re: XMLHttpRequest and Google Chrome Martin Honnen <mahotrash@yahoo.de> - 2015-04-13 11:30 +0200
    Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 11:50 +0100
      Re: XMLHttpRequest and Google Chrome Tim Streater <timstreater@greenbee.net> - 2015-04-13 13:17 +0100
        Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 13:34 +0100
          Re: XMLHttpRequest and Google Chrome Tim Streater <timstreater@greenbee.net> - 2015-04-13 14:26 +0100
          Re: XMLHttpRequest and Google Chrome Martin Honnen <mahotrash@yahoo.de> - 2015-04-13 16:15 +0200
            Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 16:03 +0100
              Re: XMLHttpRequest and Google Chrome Martin Honnen <mahotrash@yahoo.de> - 2015-04-13 19:26 +0200
                Re: XMLHttpRequest and Google Chrome "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-04-13 20:23 +0200
          Re: XMLHttpRequest and Google Chrome Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-04-13 15:50 +0100
            Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 16:10 +0100
              Re: XMLHttpRequest and Google Chrome "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-04-13 17:46 +0200
                Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 17:28 +0100
                Re: XMLHttpRequest and Google Chrome "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-04-13 19:14 +0200
                Re: XMLHttpRequest and Google Chrome Tim Streater <timstreater@greenbee.net> - 2015-04-13 18:29 +0100
                Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 18:59 +0100
                Re: XMLHttpRequest and Google Chrome "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-04-13 20:29 +0200
                Re: XMLHttpRequest and Google Chrome Tim Streater <timstreater@greenbee.net> - 2015-04-13 19:34 +0100
                Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 20:11 +0100
                Re: XMLHttpRequest and Google Chrome "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-04-13 20:44 +0200
                Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 20:21 +0100
                Re: XMLHttpRequest and Google Chrome Denis McMahon <denismfmcmahon@gmail.com> - 2015-04-14 12:43 +0000
                Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-14 14:50 +0100
                Re: XMLHttpRequest and Google Chrome Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-04-14 22:51 +0200
                Re: XMLHttpRequest and Google Chrome Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-04-13 22:28 +0200
  Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-13 19:23 +0100
    Re: XMLHttpRequest and Google Chrome Tim Streater <timstreater@greenbee.net> - 2015-04-13 19:38 +0100
  Re: XMLHttpRequest and Google Chrome "Leonardo Azpurua" <leonardo@exmvps.org> - 2015-04-13 17:36 -0430
  Re: XMLHttpRequest and Google Chrome Robbie Brown <rob@example.com> - 2015-04-14 11:35 +0100
  Re: XMLHttpRequest and Google Chrome Denis McMahon <denismfmcmahon@gmail.com> - 2015-04-14 11:37 +0000

csiph-web