suggest

var suggest = function(selector) {
    selector = selector || '*';
    var self = this;
    this.getClasses = function(selector, classHint) {
        classHint = classHint || '';
        var lastClassHint = classHint.substr(classHint.lastIndexOf('.') + 1);
        classHint = classHint.replace(/\.$/, '');
        var classHintRegex = new RegExp('^' + classHint.replace(/\./, ''));
        var res = {};
        var els = document.querySelectorAll(selector + classHint);
        if (els.length == 0) {
            els = document.querySelectorAll(selector);
        }
        var classNames = [];
        for (var i in els) {
            classNames = els[i].className;
            if (!classNames) {
                continue;
            }
            classNames = classNames.split(' ');
            for (var i in classNames) {
                if (classHintRegex.test(classNames[i])) {
                    res[classNames[i]] = true;
                }
                if (lastClassHint == '') {
                    res[classNames[i]] = true;
                }
            }
        }
        return res;
    };
    this.getIds = function(selector, idHint) {
        idHint = idHint || '';
        var idHintRegex = new RegExp('^' + idHint);
        var res = {};
        var els = document.querySelectorAll(selector);
        var id = null;
        for (var i in els) {
            id = els[i].id || null;
            if (!id) {
                continue;
            }
            if (idHintRegex.test(id)) {
                res[id] = true;
            }
        }
        return res;
    };
    this.getInnerTags = function(selector) {
        var res = {};
        if (selector.charAt(selector.length - 1) == '>') {
            selector += '*';
        }
        var innerTagName = selector.substr(selector.lastIndexOf('>') + 1);
        var innerTagNameRegex = tagName == '*' ? null : new RegExp('^' + innerTagName, 'i');
        els = document.querySelectorAll(selector);
        if (els.length == 0) {
            selector = selector.substr(0, selector.lastIndexOf('>')) + '>*';
            els = document.querySelectorAll(selector);
        }
        for (var i in els) {
            if (!els[i].tagName) {
                continue;
            }
            if (innerTagName == '*') {
                res[els[i].tagName] = true;
                continue;
            }
            if (innerTagNameRegex.test(els[i].tagName)) {
                res[els[i].tagName] = true;
            }
        }
        return res;
    };
    this.getLastType = function(obj) {
        var key = '';
        var highest = -1;
        for (var i in obj) {
            if (obj[i] > highest) {
                highest = obj[i];
                key = i;
            }
        }
        return key;
    };
    var res = {
        tags: {},
        classes: {},
        ids: {}
    }
    var lastTypePositions = {
        dot: selector.lastIndexOf('.'),
        hash: selector.lastIndexOf('#'),
        arrow: selector.lastIndexOf('>')
    }
    var lastType = getLastType(lastTypePositions);
    var lookingFor = 'tag';
    if (lastType == 'dot') {
        lookingFor = 'class';
    }
    if (lastType == 'hash') {
        lookingFor = 'id';
    }
    if (lastType == 'arrow') {
        lookingFor = 'innerTag';
    }
    var selector = selector.replace(/( )*>\1*/g, '>').split(' ');
    var selectorString = '';
    var els = null;
    for (var i in selector) {
        if (i < selector.length - 1) {
            selectorString += selector[i] + ' ';
            continue;
        }
        var tagName = selector[i].match(/^[a-z0-9>*]+/i);
        tagName = !tagName ? '*' : tagName[0];
        var tagNameRegex = tagName == '*' ? null : new RegExp('^' + tagName, 'i');
        var classString = selector[i].match(/\.[a-z0-9\-_.]+/i);
        classString = !classString ? '' : classString[0];
        var id = selector[i].match(/#[a-z0-9\-_]+/i);
        id = !id ? '' : id[0];
        if (lookingFor == 'tag') {
            els = document.querySelectorAll(selectorString + tagName);
            if (els.length == 0) {
                els = document.querySelectorAll('*');
            }
            var tmp = {};
            for (var i in els) {
                if (!els[i].tagName) {
                    continue;
                }
                tmp[els[i].tagName] = true;
            }
            if (Object.keys(tmp).length == 1) {
                els = document.querySelectorAll('*');
            }
            for (var i in els) {
                if (!els[i].tagName) {
                    continue;
                }
                if (tagName == '*') {
                    res.tags[els[i].tagName] = true;
                    continue;
                }
                if (tagNameRegex.test(els[i].tagName)) {
                    res.tags[els[i].tagName] = true;
                }
            }
        }
        if (lookingFor == 'class') {
            var classes = self.getClasses(tagName, classString);
            res.classes = classes;
        }
        if (lookingFor == 'id') {
            var id = selector[selector.length - 1].split('#')[1];
            var ids = self.getIds(tagName, id);
            res.ids = ids;
        }
        if (lookingFor == 'innerTag') {
            var tags = self.getInnerTags(tagName);
            res.tags = tags;
        }
    }
    return res;
}