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document updated 15 years ago, on Mar 2, 2009

One REALLY CONSTANTLY useful thing that jQuery is good for is an "enhanced CSS parser". Cross-browser support for CSS3 selectors is really limited, so something like this ends up in lots of headers (particularly for table-column settings):
```
    <script type="text/javascript" src="/js/jquery.js"></script>
    <script type="text/javascript"> 
    $(document).ready(function() {
            $("td:nth-child(3)").addClass("number_right");
    });
    </script>
```

Another *really* useful thing is a client-side template system:

    <script type="text/javascript"> 
    $(document).ready(function() {
        $("fact").replaceWith("<sup class='template_fact'>[<i><a href='http://en.wikipedia.org/wiki/Wikipedia:Citation_needed'>citation needed</a></i>]</sup>");
    });
    $("todo").each( function() {
        var txt = $(this).attr("descr");
        $(this).empty().append("<sup class='template'>[<i>todo — <span></span></a></i>]</sup>").find('span').text( txt );
    });

    </script>

    George W. Bush is a moron.<fact />

    <todo descr='what can we do about it?' />

In this case, every <fact /> tag will be replaced with [citation needed].

While this works in all modern browsers, I've seen rumors that it fails in older browsers. Specifically that such ad-hoc elements weren't included in the final DOM parse-tree, because they were seen as superfluous. (TODO: figure out which versions)

There are several more complete "template engines" for jQuery: spin-off of Ext, textareas

$("selector").each( function(i){ ... $(this) ... } ) is something that's always useful (though are sometimes faster ways to accomplish the same thing)