jQuery in Opera User JS Doesn't Work

). I'm playing with some Opera User JS. I included "1jquery.min.js" in my User JS folder (1 in front because Opera loads them alphabetically). Unfortunately, it doesn't appear to be working.

window.onload = OnWindowLoad;

$(document).ready(function()
{
  alert ($('#area_19'));
});

function OnWindowLoad ()
{
  alert ($('#area_19'));
  alert(document.getElementById("area_19"));
}

What's interesting about this code is that the first two alerts come back in NULL, but the last one does find the object! So the 开发者_Python百科element definitely exists in the page, but my jQuery seems unable to get it. What's even stranger is that the jQuery "ready" function works, indicating that I do have jQuery capability.

I'm quite puzzled about all this ::- /. Hopefully somebody can give me a clue ::- ).

I suspect you are running the script on a page that uses another JS framework, probably Prototype.js.

If Prototype were included by the target page it would overwrite your jQuery copy of $ with its own that gets an element by ID, not selector. Since there is no element with ID #area_19 (# not being a valid character in an ID), it would return null. jQuery would never return null for a non-existant element, you'd only get an empty wrapper object.

(The $(document).ready() code would still execute because the $ was called before Prototype was included and changed the behaviour of $.)

Try using the explicit jQuery function rather than the $ shortcut.

These sorts of interferences are common when mixing multiple frameworks, or even mixing two copies/versions of the same framework. From jQuery's side its interactions can be reduced, but not eliminated, with noConflict. Personally for code like user scripts that might have to live in a wide range of contexts not controlled by myself, I would avoid using wide-ranging frameworks like jQuery.