来自腾讯的一个不固定高度得消息的滚动特效

var $ = function (d){
typeof d == "string" &&(d = document.getElementById(d));
return $.fn.call(d);
};
$.fn = function (){
this.addEvent = function (sEventType,fnHandler){
if (this.addEventListener) {this.addEventListener(sEventType, fnHandler, false);}
else if (this.attachEvent) {this.attachEvent("on" + sEventType, fnHandler);}
else {this["on" + sEventType] = fnHandler;}
}
this.removeEvent = function (sEventType,fnHandler){
if (this.removeEventListener) {this.removeEventListener(sEventType, fnHandler, false);}
else if (this.detachEvent) {this.detachEvent("on" + sEventType, fnHandler);}
else { this["on" + sEventType] = null;}
}
return this;
};
var Class = {create: function() {return function() { this.initialize.apply(this, arguments); }}};
var Bind = function (obj,fun,arr){return function() {return fun.apply(obj,arr);}}
var Marquee = Class.create();
Marquee.prototype = {
initialize: function(id,name,out,speed) {
this.name = name;
this.box = $(id);
this.out = 3;//滚动间隔时间,单位秒
this.speed = speed;
this.d = 1;
this.box.style.position = "relative";
this.box.scrollTop = 0;
var _li = this.box.firstChild;
while(typeof(_li.tagName)=="undefined")_li = _li.nextSibling;
this.lis = this.box.getElementsByTagName(_li.tagName);
this.len = this.lis.length;
for(var i=0;i=this.box.offsetHeight)break;
}
this.Start();
this.box.addEvent("mouseover",Bind(this,function(){clearTimeout(this.timeout);},[]));
this.box.addEvent("mouseout",Bind(this,this.Start,[]));
},
Start:function (){
clearTimeout(this.timeout);
this.timeout = setTimeout(this.name+".Up()",this.out*1000)
},
Up:function(){
clearInterval(this.interval);
this.interval = setInterval(this.name+".Fun()",10);
},
Fun:function (){
this.box.scrollTop+=this.speed;
if(this.lis[this.d].offsetTop = this.len + 1){
this.d = 1;
this.box.scrollTop = 0;
}
}
};
$(window).addEvent("load",function (){
marquee = new Marquee("msg_weibo","marquee",1,2);
});

[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]

看关键的js code：


代码如下:

var $ = function (d){
typeof d == "string" &&(d = document.getElementById(d));
return $.fn.call(d);
};
$.fn = function (){
this.addEvent = function (sEventType,fnHandler){
if (this.addEventListener) {this.addEventListener(sEventType, fnHandler, false);}
else if (this.attachEvent) {this.attachEvent("on" + sEventType, fnHandler);}
else {this["on" + sEventType] = fnHandler;}
}
this.removeEvent = function (sEventType,fnHandler){
if (this.removeEventListener) {this.removeEventListener(sEventType, fnHandler, false);}
else if (this.detachEvent) {this.detachEvent("on" + sEventType, fnHandler);}
else { this["on" + sEventType] = null;}
}
return this;
};
var Class = {create: function() {return function() { this.initialize.apply(this, arguments); }}};
var Bind = function (obj,fun,arr){return function() {return fun.apply(obj,arr);}}
var Marquee = Class.create();
Marquee.prototype = {
initialize: function(id,name,out,speed) {
this.name = name;
this.box = $(id);
this.out = 3;//滚动间隔时间,单位秒
this.speed = speed;
this.d = 1;
this.box.style.position = "relative";
this.box.scrollTop = 0;
var _li = this.box.firstChild;
while(typeof(_li.tagName)=="undefined")_li = _li.nextSibling;
this.lis = this.box.getElementsByTagName(_li.tagName);
this.len = this.lis.length;
for(var i=0;i<this.lis.length;i++){
var __li = document.createElement(_li.tagName);
__li.innerHTML = this.lis[i].innerHTML;
this.box.appendChild(__li);//cloneNode
if(this.lis[i].offsetTop>=this.box.offsetHeight)break;
}
this.Start();
this.box.addEvent("mouseover",Bind(this,function(){clearTimeout(this.timeout);},[]));
this.box.addEvent("mouseout",Bind(this,this.Start,[]));
},
Start:function (){
clearTimeout(this.timeout);
this.timeout = setTimeout(this.name+".Up()",this.out*1000)
},
Up:function(){
clearInterval(this.interval);
this.interval = setInterval(this.name+".Fun()",10);
},
Fun:function (){
this.box.scrollTop+=this.speed;
if(this.lis[this.d].offsetTop <= this.box.scrollTop){
clearInterval(this.interval);
this.box.scrollTop = this.lis[this.d].offsetTop;
this.Start();
this.d++;
}
if(this.d >= this.len + 1){
this.d = 1;
this.box.scrollTop = 0;
}
}
};
$(window).addEvent("load",function (){
marquee = new Marquee("msg_weibo","marquee",1,2);
});

实现思路与以前的文字滚动是一样的，都是先充满当前容器，再通过scrollTop++往上滚的，只不过他是每次滚动的距离不是固定的，是取当前滚动消息的高度。由于scrollTop（滚出当前可视区域的高度）和offsetTop（距离父节点顶部的距离，常用于取某元素在页面的坐标位置）的区别，所以通过 if(this.lis[this.d].offsetTop <= this.box.scrollTop)来判断是否滚动完上条消息，需要停顿下了。

我觉得亮点之处在于$的写法。通常Prototype里也就取下obj||document.getElementById('objId')，他这里除此外还帮obj绑定了一些方法。他的作用是不是类似于原型扩展String、Array等对象的方法呢。这个可以借鉴。
另外，他初始化时填充容器时用document.createElement->赋innerHTML->appendChild来做，我觉的不如直接cloneNode(true)->appendChild好，如不对，欢迎指正。

主要还是填下这个月的坑，哈哈。