cssWalker.js

/*	cssWalker.js 
 *	
 *	Traverse every stylesheet in the document and filter based on their selectors.
 *
 *	@Requires: Nothing, completely standalone.
 *
 *	@Returns: An array of style objects/rules. The order of the array is determined by the point
 *		of the stylesheet in the document - e.g, first stylesheet rules are top of the array.
 *
 *	@Author: Ryan McGrath (ryan@webs.com)
 */
var cssWalker = {
	
	/*	cssWalker.find({...});
	 *	
	 *	The only function you need to worry about. Usage is something like below:
	 *
	 *	var lol = cssWalker.find({
	 *		styleSheet: <optional; will take an existing stylesheet and parse only that>,
	 *		selector: ".css_selector_example",
	 *		exclude: "A string of selectors to exclude - e.g, we'll take anything that matches 'html' but doesn't have 'div'.
	 *			To do multiples of these, separate them by pipes, ala... b|a|em|strong|etc"
	 *	});
	 *
	 */
	find: function(params) {
		var results = [],
			styleSheets = typeof params.styleSheet === "undefined" ? document.styleSheets : params.styleSheet;

		if(styleSheets.length === "undefined") {			
			return cssWalker._locate({
				styleSheet: params.styleSheet,
				selector: params.selector,
				exclude: params.exclude ? params.exclude : false
			});
		} else {
			for(var i = 0; i < styleSheets.length; i++) {
				var extendedResults = cssWalker._locate({
					styleSheet: styleSheets[i],
					selector: params.selector,
					exclude: params.exclude ? params.exclude : false
				});

				results = results.concat(extendedResults);
			}
			return results.reverse();
		}
	},

	/*	cssWalker._locate({...});
	 *
	 *	The internal (private) function/engine that actually handles lookups and traversals.
	 *	Param object/arguments are the same as cssWalker.find(), see above for notes.
	 */
	_locate: function(params) {
		var styleSheet = params.styleSheet,
			declarations = styleSheet.cssRules ? styleSheet.cssRules : styleSheet.rules,
			results = [];

		for(var i = 0; i < declarations.length; i++) {
			var selector = declarations[i].selectorText.toLowerCase();

			if(selector.indexOf(params.selector) != -1) {
				if(params.exclude) {
					var exclusions = params.exclude.split("|"),
						shouldPush = true;

					for(var t = 0; t < exclusions.length; t++) {
						if(selector.indexOf(exclusions[t]) >= 0) shouldPush = false;  
					}

					if(shouldPush) results.push(declarations[i]);
				} else {
					results.push(declarations[i]);
				}
			}
		}

		return results;
	} 
};