<Meta charset="UTF-8">

1F男装
• 2F女装
• 3F美妆
• 4F数码
• 5F母婴

//定义getByClassName函数，让函数实现根据className获取对象并返回 function getByClassName(obj,cls) { var elements = obj.getElementsByTagName("*"); var result = []; for (var i = 0; i < elements.length; i++) { if (elements[i].className == cls) { result.push(elements[i]); } } return result; } //定义hasClass函数，确认对象是否包含对应的class function hasClass(obj,cls) { return obj.className.match(new RegExp("(\\s|^)" + cls + "(\\s|$)")); } //定义removeClass函数，让函数实现删除对象的class function removeClass(obj,cls) { if (hasClass(obj,cls)) { //remove var reg = new RegExp("(\\s|^)" + cls + "(\\s|$)"); obj.className = obj.className.replace(reg,""); } } //定义addClass函数，让函数实现给对象增加class function addClass(obj,cls) { if (!hasClass(obj,cls)) { obj.className += " " + cls; } } //页面加载完毕执行以下函数 window.onload = function() { //页面滚动时，执行以下函数 window.onscroll = function() { var top = document.documentElement.scrollTop || document.body.scrollTop; var menus = document.getElementById("menu").getElementsByTagName("a"); var items = getByClassName(document.getElementById("content"),"item"); var currentId = ""; for (var i = 0; i < items.length; i++) { var _item = items[i]; var _itemTop = _item.offsetTop; if (top > _itemTop - 200) { currentId = _item.id; } else { break; } } //给正确的menu下的a元素class赋值current if (currentId) { for (var j = 0; j < menus.length; j++) { var _menu = menus[j]; var _href = _menu.href.split("#"); if (_href[_href.length - 1] != currentId) { removeClass(_menu,"current"); } else { addClass(_menu,"current"); } } } } }