8月最后1天,赶紧补篇博客。贴个最近看到的腾讯的特效,写的还可以。先看效果。


 

看关键的js code:

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。

posted on 2010-08-31 22:44  JayChow  阅读(1822)  评论(1编辑  收藏  举报