从网易扒过来的js调用广告显示文件(随机几率)

从网易撬过来的js调用广告显示文件
只有下面短短几行代码可以随机显示flash和gif广告，还不错

function column02(imgSource,url,chance,type) { 
this.imgSource = imgSource; 
this.url = url; 
this.chance = chance; 
this.type = type; 
} 
function dispColumn02() { 
with (this) 
switch (type){ 
case "img": 
document.write("<A HREF=" + url + " target=_blank><IMG SRC=" + imgSource + " WIDTH=480 HEIGHT=250 BORDER=0></A>"); 
break; 
case "html": 
document.write("<IFRAME WIDTH=480 HEIGHT=250 MARGINWIDTH=0 MARGINHEIGHT=0 HSPACE=0 VSPACE=0 FRAMEBORDER=0 SCROLLING=no BORDERCOLOR=#000000 SRC="+ imgSource + "></iframe>"); 
break; 
case "flash": 
document.write("<embed src="+imgSource+" quality=high width=480 height=250 type=application/x-shockwave-flash pluginspage=http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash></embed>"); 
break; 
default: 
document.write(""); 
} 
} 
column02.prototype.dispColumn02 = dispColumn02; 
columns02 = new Array(); 
// flash , html , img 代表三种不同的广告模式 
// 200 之类的数目是设置出现的机率 
columns02[0] = new column02("http://smsimg.163.com/honey/honey_ad.swf","",200,"flash");//主广告 
columns02[1] = new column02("http://smsimg.163.com/honey/honey_photo.swf","",800,"flash"); //上传图片免月租 
columns02[2] = new column02("http://smsimg.163.com/honey/honey_gold.swf","",800,"flash"); //登陆送金币 
//columns02[] = new column02("f","",100,"");// （20030422～20030722） 
sum_of_all_chances = 0; 
for (i = 0; i < columns02.length; i++) { 
sum_of_all_chances += columns02[i].chance; 
} 
function randomColumn02() { 
chance_limit = 0; 
randomly_selected_chance = Math.round((sum_of_all_chances - 1) * Math.random()) + 1; 
for (i = 0; i < columns02.length; i++) { 
chance_limit += columns02[i].chance; 
if (randomly_selected_chance <= chance_limit) { 
columns02[i].dispColumn02(); 
break; 
} 
} 
} 
this_column02 = randomColumn02();

脚本之家测试代码，chance越大显示的几率越大


function jb51(url,chance) {
this.url=url;
this.chance=chance;
}
var da,dalen,chance_limit,random_sel_num
da=new Array();
da[0]=new jb51("http://www.baidu.com",200)
da[1]=new jb51("http://www.jb51.net",600)
da[2]=new jb51("http://sc.jb51.net",800)
var dalen=da.length;
num_all_chance=0;
for(i=0;i