Hi Fred,
No, not in standard JavaScript. The interpreter will work its way up
the scope chain looking for "Prototype"; if it reaches the global
object (which is always the root of the scope chain; the global object
in browser apps is the window object), it assumes the reference is a
property of that object. The property will have the value undefined.
That's why people keep getting into trouble with implicit global
variables (e.g., forgetting to declare them), like this:
function foo(stringArray)
{
for (i = 0; i < myArray.length; ++i)
{
bar(stringArray);
}
}
function bar(element)
{
i = element.indexOf(',');
if (i > 0)
{
$(element.substring(0, i)).update(element.substring(i + 1));
}
}
Since 'i' isn't declared anywhere, it implicitly becomes a property of
the global object (window), and hence the above code blows up because
the 'i' in foo() and the 'i' in bar() are the same property
(window.i), and so bar() stomps on the array iterator in foo().
More in my sadly-neglected blog:
http://blog.niftysnippets.org/2008/03/horror-of-implicit-globals.html
--
T.J. Crowder
tj / crowder software / com
On Jun 7, 6:00 pm, "Frederick Polgardy" <[EMAIL PROTECTED]> wrote:
> I thought this would throw an exception if Prototype wasn't defined. You
> would need to say:
>
> var Prototype
> if (Prototype) { ... }
>
> Right?
>
> -Fred
>
>
>
> On Sat, Jun 7, 2008 at 1:58 AM, T.J. Crowder <[EMAIL PROTECTED]> wrote:
>
> > Or "if (Prototype) { ... }" ?
> > --
> > T.J. Crowder
> > tj / crowder software / com
>
> > On Jun 6, 10:12 pm, kangax <[EMAIL PROTECTED]> wrote:
> > > typeof unfortunately returns "object" when applied to null
> > > typeof null; // "object"
>
> > > A safer way is to test for undefined:
>
> > > if (typeof Prototype != 'undefined') {
> > > ...
>
> > > }
>
> > > - kangax
>
> > > On Jun 6, 4:35 pm, nlloyds <[EMAIL PROTECTED]> wrote:
>
> > > > On Jun 4, 1:50 pm, sheps-ii <[EMAIL PROTECTED]> wrote:
>
> > > > > Thank you, that's fantastic. I love how prototype helps true
> > > > > modularity into content(server side)->structure (html)->behaviour
> > > > > (js). Cheers!
>
> > > > To take it a step further, I usually encapsulate everything in a class
> > > > or namespace. So, the bottom of the html looks like this:
>
> > > > <script type="text/javascript" src="prototype.js"></script>
> > > > <script type="text/javascript" src="mysite.js"></script>
> > > > </body>
> > > > </html>
>
> > > > Then the mysite.js:
>
> > > > if (typeof Prototype == "object") { // only load if Prototype is
> > > > present
> > > > var MySite = Class.create({
> > > > initialize : function () {
> > > > ... // stuff to do on page load
>
> > > > this.addObservers();
> > > > },
>
> > > > // Add additional event handlers here
> > > > addObservers : function () {
> > > > ...
> > > > },
>
> > > > ...
>
> > > > });
> > > > document.observe("dom:loaded", function () { new MySite() });
>
> > > > }
>
> > > > I don't know if that's the best way to do things, but It works well
> > > > for me. YMMV
>
> --
> Science answers questions; philosophy questions answers.
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