Finding all classes that match a pattern in an HTML document?

Question

I got to thinking today: what is the best way of getting a distinct (ie no repeats) list of classes used in a document that (preferably) match a pattern (regular expression) pattern or (alternatively) start with a certain character sequence? JQuery can be used for this or just straight Javascript.

Now it should obviously cater for all legal class usages, for example:

<div class="class1 class2 class3">
</div>

And I don't want to parse the document with regular expressions. That's simply too error prone. What I'm interested in is a Jaavascript solution that walks the DOM or uses something like jQuery to do that.

Oh this should also include any classes that have been dynamically added/removed through previous Javascript code.

Suggestions?

Answer 1

function gatherClasses() {
    var tags = document.getElementsByTagName('*');
    var cls, clct = {}, i, j, l = tags.length;
    for( i = 0; i < l; i++ ) {
        cls = tags[i].className.split(' ');
        for( j = 0; j < cls.length; j++ ) {
            if( !cls[j] ) continue;
            clct[cls[j]] = 'dummy'; //so we only get a class once
        }
    }
    cls = [];
    for( i in clct ) {
        cls.push( i );
    }
    return cls;
} 
alert(gatherClasses())

Heres a version with a regexp match

function gatherClasses( matchString ) {
    if( matchString ) {
        var rxp = new RegExp( matchString );
    } else {
        var rxp = /.*/;
    }
    var tags = document.getElementsByTagName('*');
    var cls, clct = {}, i, j, l = tags.length;
    for( i = 0; i < l; i++ ) {
        cls = tags[i].className.split(' ');
        for( j = 0; j < cls.length; j++ ) {
            if( !cls[j] || !rxp.test( cls[j] ) ) {
                continue;
            }
            clct[cls[j]] = 'dummy'; //so we only get a class once
        }
    }
    cls = [];
    for( i in clct ) {
        cls.push( i );
    }
    return cls;
}
//find classes that match 'stack'
alert(gatherClasses('stack'))

Answer 2

Can this help you?

http://httpcode.com/blogs/PermaLink,guid,77f17d9c-cdc0-4fcb-a392-3cc70ef6ac23.aspx

<input type="radio" class="star star_id_45 star_group_5" />

$("input[class*='star_id_45']")