Javascript for harvesting computed styles on a page

cssRules.js

var cssRules = function(){
    var filter = Array.prototype.filter;
    var map = Array.prototype.map;
    var rules = map.call(document.querySelectorAll('*'), function(element){
        return element.ownerDocument.defaultView.getMatchedCSSRules(element,'');
    });

    var items = rules.map(function(list){
        list = list || [];
        return map.call(list, function(rule){
            return rule.cssText;
        });
    });

    var flattened = items.reduce(function(a, b) {
        return a.concat(b);
    });

    var rules = flattened.filter(function(value, index, arr){
        return arr.indexOf(value) === index;
    });

    var sheets = filter.call(document.styleSheets, function(sheet){
        return sheet.rules;
    });

    var _rules = sheets.map(function(sheet){
        return filter.call(sheet.rules, function(rule){

            // regex for pseudo - /^[\#\.\w\ ]*\:+:?[\#\.\w\-\(\)]*[\,\{\ ]*$/
            return rule.cssText.indexOf(':hover') > -1 ||
                rule.cssText.indexOf(':active') > -1 ||
                rule.cssText.indexOf(':focus') > -1 ||
                rule.cssText.indexOf(':visited') > -1 ||
                rule.cssText.indexOf(':link') > -1 ||
                rule.cssText.indexOf(':first-child') > -1 ||
                rule.cssText.indexOf(':nth-child') > -1 ||
                rule.cssText.indexOf(':last-child') > -1 ||
                rule.cssText.indexOf(':before') > -1 ||
                rule.cssText.indexOf(':after') > -1 ||
                rule.cssText.indexOf('::before') > -1 ||
                rule.cssText.indexOf('::after') > -1 ||
                rule.cssText.indexOf(':first-line') > -1 ||
                rule.cssText.indexOf(':first-letter') > -1 ||
                rule.cssText.indexOf('::first-line') > -1 ||
                rule.cssText.indexOf('::first-letter') > -1 ||
                rule.cssText.indexOf('menu') > -1;


        });
    });
    _rules = _rules.reduce(function(a, b) {
        return a.concat(b);
    });

    _rules = _rules.map(function(rule){
        return rule.cssText;
    });

    _rules.forEach(function(item){
        rules.push(item);
    });

    return rules;
};