// 悬浮置顶; (function ($) {    $.fn.crumbsFixedPosition = function (options) {        var defaults = {            cName: ‘fixed_pos‘        }        var options = $.extend(defaults, options);        return this.each(function () {            var $this = $(this);            var t = $(this).offset().top;            $(window).on(‘scroll‘, function () {                if ($(this).scrollTop() > t) {                                        $this.addClass(options.cName);                } else {                    $this.removeClass(options.cName);                }            });        });    };})(jQuery);$(function () {    $(‘.curr_pos‘).crumbsFixedPosition();});

// 返回顶部; (function ($) {    $.fn.backToTop = function (options) {        var defaults = {            t: 200        }        var options = $.extend(defaults, options);        return this.each(function () {            var $this = $(this);            $this.append(‘<div class="backToTop"><span>返回顶部</span></div>‘);            var $o = $this.find(‘.backToTop‘);            $(window).on(‘scroll resize‘, function () {                if ($(document).scrollTop() > 0) {                    $o.fadeIn();                } else {                    $o.fadeOut();                }            });            $o.on({                ‘click‘: function () {                        $(‘body,html‘).stop(true, false).animate({ scrollTop: 0 }, options.t);                },                ‘selectstart‘: function () {                    return false;                }            });        });    };})(jQuery);$(function () {    $(‘body‘).backToTop();});

(1)<script type="text/javascript">       function foo(){            var str = ‘a,b,c,d,e,f,g‘;            var s = reverse(str);//字符串反转            console.log(s);            if(s === ‘g,f,e,d,c,b,a‘){                console.log(‘成功。‘);            }else{                console.log(‘失败。‘);            }        }        function reverse(str){            var sp = str.split(‘,‘);            //保存反转之后的字符串            var new_str = ‘‘;            /*从后往前取，用逗号分隔*/            for(var i = sp.length-1;i>=0;i--){                new_str += sp[i]+‘,‘;            }            /*取到length-1，否则会取到最后一个逗号。*/            new_str = new_str.substring(0,new_str.length-1);            return new_str;        }    </script>(2)<script type="text/javascript">        function foo(){            var str = ‘a,b,c,d,e,f,g‘;            var s = reverse(str);            if(s == ‘g,f,e,d,c,b,a‘){                alert(‘成功。‘);            }            else{                alert(‘失败。‘);            }        }        function reverse(str){            return str.split(‘,‘).reverse().join(‘,‘);        }    </script>