jQuery选择器的性能测试

在https://github.com/doomhz/jQuery-Tweaks 上面看到jQuery性能测试工具：

[javascript]
/**
* Doom Tweaks for Javascript Projects
*
* @author Dumitru Glavan
* @version 1.1 (16-JUL-2011)
* @requires jQuery
* @link http://dumitruglavan.com
*
* @example: $.l(4,5,6);
* @example: $.time();
* @example: $.lt();$('div')$.lt();
* @example: $.bm('$('div')'); - benchmark your code
* @example: $.mockAjax({mockUrl: '/ajax_mocks'}); - mock your ajax calls
*
* Dual licensed under the MIT and GPL licenses:
*   http://www.opensource.org/licenses/mit-license.php
*   http://www.gnu.org/licenses/gpl.html
*
*/ 
(function ($) { 
 
    /**
     * Extend Firebug
     */ 
    if (typeof(console) === 'object') { 
        /**
         * Shortcut function for console.log()
         */ 
        $.extend($, { 
            l: function () { 
                for (var i = 0; i < arguments.length; i++) { 
                    console.log(arguments[i]); 
                } 
            } 
        }); 
    } 
 
    /**
     * Shortcut function for getting timestamp in second (PHP like function time())
     * @param numeric divideBy - You can switch back to milliseconds by specifying this as 1
     */ 
    $.extend($, { 
        time: function (divideBy) { 
            return ~~(+ (new Date().getTime() / (typeof divideBy === 'undefined' ? 1000 : divideBy))); 
        } 
    }); 
 
    /**
     * Shortcut function for logging time to the Firebug console
     * call $.lt() then your code then $.lt() again to get the results
     */ 
    $.extend($, { 
        lt: function () { 
            if (this.ltLastTime == null) {