0 Regexes

0 Try-catch blocks

0 Browser sniffing

Puma is a new, speedy, CSS selector engine. Extremely lightweight and easily droppable into any library, Puma supports all CSS2 and most CSS3 selectors.

It's syntax is just like Sizzle and friends:

Puma(selector[, DOMElement])

It's also very extensible: you can add new pseudoclasses or operators any time you want. Let's say we want to define the @ operator for matching the rel attribute:

Puma.operators.binary['@'] = function (left, right, context) {
    return Puma.arrayFilter(left.evaluate(context), function (e) {
        return e.getAttribute('rel') == right.value;
    });
};

This code simply evaluates the left side of the parse tree and reduces it to the elements with the specified value for the rel attribute. You can use it like div@stuff or img[src^="/assets/images"]@myrel.theClass.

To add it as a unary operator so you can use it like @cake, you can simply do:

Puma.operators.unary['@'] = function (right, context) {
    return Puma.operators.binary['@'](new Puma.AST.Tag('*'), right, context);
}

More documentation on extension will be available sometime when I get around to it (hopefully within the next few years :-P).