I can get simple examples to work fine as long as there's no master page involved. All I want to do is click a button and have it say "hello world" with the javascript in a .js file, using a master page. Any help very much appreciated :)
EDIT
As @Adam points out in the comments, there is a native jQuery mechanism that basically does the same thing as the hack in my original answer. Using jQuery you can do
$('[id$=myButton]').click(function(){ alert('button clicked'); });
My hack was originally developed as a Prototype work around for ASP.NET and I adapted it for the original answer. Note that jQuery basically does the same thing under the hood. I recommend using the jQuery way, though, over implementing my hack.
Original answer left for comment context
When you use a master page, ASP.NET mangles the names of the controls on the dependent pages. You'll need to figure out a way to find the right control to add the handler to (assuming you're adding the handler with javascript).
I use this function to do that:
function asp$( id, tagName ) {
var idRegexp = new RegExp( id + '$', 'i' );
var tags = new Array();
if (tagName) {
tags = document.getElementsByTagName( tagName );
}
else {
tags = document.getElementsByName( id );
}
var control = null;
for (var i = 0; i < tags.length; ++i) {
var ctl = tags[i];
if (idRegexp.test(ctl.id)) {
control = ctl;
break;
}
}
if (control) {
return $(control.id);
}
else {
return null;
}
}
Then you can do something like:
jQuery(asp$('myButton','input')).click ( function() { alert('button clicked'); } );
where you have the following on your child page
<asp:Button ID="myButton" runat="server" Text="Click Me" />