On Oct 9, 2011, at 5:17 AM, T.J. Crowder wrote:
> Hi,
>
> On Oct 8, 6:30 pm, Walter Lee Davis <wa...@wdstudio.com> wrote:
>> What's a more idiomatic way to write this:
>>
>> Element.addMethods({
>> toggleClassName: function(element, className){
>> var element = $(element);
>> (element.hasClassName(className)) ?
>> element.removeClassName(className) : element.addClassName(className);
>> return element;
>> }
>>
>> });
>>
>> This works, but it's got that really long line in the middle. How do you do
>> what PHP calls a "variable variable" in JavaScript to execute the correct
>> method (add/remove) based on the input without writing it all out long-hand?
>>
>> Walter
>
> You are aware that Prototype *has* `toggleClassName` already[1],
> right? And in fact, I think the current implementation of it answers
> your question about "variable variables":
>
> toggleClassName: function(element, className) {
> if (!(element = $(element))) return;
> return Element[Element.hasClassName(element, className) ?
> 'removeClassName' : 'addClassName'](element, className);
> },
>
> That works because as you probably know, you can refer to an object
> property using a literal with dotted syntax:
>
> x = obj.foo;
>
> ...or with a string using bracketed syntax:
>
> x = obj['foo'];
>
> The latter opens up the possibility of using an expression for the
> string:
>
> x = obj[flag ? 'foo' : 'bar'];
>
> And of course, what we think of as methods aren't really methods at
> all[2], they're just functions assigned to properties, and so:
>
> obj[flag ? 'foo' : 'bar']();
>
> ...will call `obj.foo()` or `obj.bar()` depending on the value of
> `flag`. That's what the Prototype version of `toggleClassName` does,
> it calls `removeClassName` or `addClassName` based on the result of
> calling `hasClassName`.
>
> This form of "variable variables" only works with object properties,
> but I find that it applies in 99% of the situations I'd want it.
>
> [1] http://api.prototypejs.org/dom/Element/toggleClassName/
> [2] http://blog.niftysnippets.org/2008/03/mythical-methods.html
>
> HTH,
> --
> T.J. Crowder
> Independent Software Engineer
> tj / crowder software / com
> www / crowder software / com
Wow. FacePalm! Thanks very much, I'd been re-doing this long-hand since 1.4,
never realized it was "native".
Walter
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