Re: DOM event flow

On 24/05/2006 11:16, Spartanicus wrote:

In trying to take it one step further I'd like the function to
execute only when the window width changes.

The code only needs slight modification:

this.onload = function() {
var width = document.body.clientWidth;

document.body.onresize = function() {
if (document.body.clientWidth != width)
location.reload();
};
};

First I should illustrate what I'm trying to do.

Opera has a preliminary implementation of CSS3 media queries, this allows dissolving a multi column layout for narrower window widths. Currently the CSS media query isn't reevaluated on a window resize,
it requires a reload [...]

Has that been reported to Opera? I don't know if the query /must/ be re-evaluated, but it certainly should be.

[snip]

After a glance in a JS book

Based upon informed third-party opinion, most books on scripting are rubbish, unfortunately. I've never read any myself, but the other regulars in c.l.javascript can just about recommend "JavaScript: The Definitive Guide, 4th Edition"[1] (and some may only consider that the least bad, rather than good).

and not hindered by a proper understanding of JS & the DOM

:-)

I tried:

<script type="text/javascript">
window.innerWidth.onresize = function() {
location.reload(false);
};

[snip]

Even if that onresize property persisted (see below), the innerWidth property is not an element, it would not receive events, and so the function would never be executed.

<off-topic>
The innerWidth property of the global object is simply a number (where implemented) and has no members, nor can it be assigned any.

To illustrate the latter point, consider:

var number = 10;

number.property = 'value';
alert(typeof number.property);

The alert will contain 'undefined', not 'string'. The reason is that only objects have properties. Though one may use methods with primitives, what goes on behind the scenes is a little complex than it may otherwise appear. For example,

var message = 'Hello %s!';

alert(message.replace('%s', 'World'));

message is a string primitive, but the code would still display 'Hello World!'. What is actually happening is that in using dot notation, the left-hand operand is implicitly converted to an object, similar to:

Object(message).replace(...)

which is equivalent (in this instance) to:

(new String(message)).replace(...)

The same thing occurs when trying to create a property on a primitive, but because the implicitly created object is only temporary, the new property disappears along with the object itself.

In the code you posted, a Number object will be created using the innerWidth property, and a reference to a function object will be assigned to a new property, onresize. However, because there are no references to it, this Number object will be marked for garbage collection, and the function object will soon follow suit.
</>

Hope that helps,
Mike


[1] Recommended books, c.l.javascript FAQ
<http://www.jibbering.com/faq/#FAQ3_1>

--
Michael Winter
Prefix subject with [News] before replying by e-mail.
.

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