Set classes on an element from an object

updateClasses.js

function updateClasses(el, options) {
    var classes = el.className.split(/\s+/),
        className,
        pattern = /^no-(\w+)$/,
        val,
        i, l;

    for (i = 0, l = classes.length; i < l; i++) {
        className = classes[i];
        if (!options.hasOwnProperty(className)) {
            val = pattern.exec(className);
            if (val && options.hasOwnProperty(val[1])) {
                className = val[1];
            }
        }

        if (options.hasOwnProperty(className)) {
            val = options[className];
            val = 
                val == '1' || val == 'true' ? true :
                val == '0' || val == 'false' ? false :
                val;

            if (typeof val == 'boolean') {
                classes[i] = val ? className : 'no-' + className;
            }
        }
    }


    el.className = classes.join(' ');
    return classes;
}

usage.js

// classes before: no-stuff things
updateClasses(document.documentElement, { stuff: true, things: false });
// classes after: stuff no-things