js漂浮广告实现代码_javascript技巧

var vmin=2;
var vmax=5;
var vr=2;
var timer1;

function iecompattest(){
return (document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body
}

function Chip(chipname,width,height){
 this.named=chipname;
 this.vx=vmin+vmax*Math.random();
 this.vy=vmin+vmax*Math.random();
 this.w=width+20;
 this.h=height;
 this.xx=0;
 this.yy=0;
 this.timer1=null;
}

function movechip(chipname){
if (document.getElementById){
eval("chip="+chipname);
  if (window.innerWidth || window.opera){
  pageX=window.pageXOffset;
   pageW=window.innerWidth-40;
   pageY=window.pageYOffset;
   pageH=window.innerHeight-20;
  }
  else if (document.body){
  pageX=iecompattest().scrollLeft;
   pageW=iecompattest().offsetWidth-40;
   pageY=iecompattest().scrollTop;
   pageH=iecompattest().offsetHeight-20;
  } 

  chip.xx=chip.xx+chip.vx;
  chip.yy=chip.yy+chip.vy;
  
  chip.vx+=vr*(Math.random()-0.5);
  chip.vy+=vr*(Math.random()-0.5);
  if(chip.vx>(vmax+vmin)) chip.vx=(vmax+vmin)*2-chip.vx;
  if(chip.vx<(-vmax-vmin)) chip.vx=(-vmax-vmin)*2-chip.vx;
  if(chip.vy>(vmax+vmin)) chip.vy=(vmax+vmin)*2-chip.vy;
  if(chip.vy<(-vmax-vmin)) chip.vy=(-vmax-vmin)*2-chip.vy;

  if(chip.xx<=pageX){
  chip.xx=pageX;
   chip.vx=vmin+vmax*Math.random();
   }
  if(chip.xx>=pageX+pageW-chip.w){
  chip.xx=pageX+pageW-chip.w;
   chip.vx=-vmin-vmax*Math.random();
   }
  if(chip.yy<=pageY)
   {chip.yy=pageY;
   chip.vy=vmin+vmax*Math.random();
   }
  if(chip.yy>=pageY+pageH-chip.h)
   {chip.yy=pageY+pageH-chip.h;
   chip.vy=-vmin-vmax*Math.random();
   }

document.getElementById(chip.named).style.left=chip.xx+"px";
document.getElementById(chip.named).style.top=chip.yy+"px";


  chip.timer1=setTimeout("movechip('"+chip.named+"')",100);
 }
}