一、案例介绍

这个案例主要是动态控制下雪，当然你也可以让他下别的，只要修改一下图片就可以了！

二、代码如下：

   thisURL = document.URL;
            function stop() {
                removeSnow();
            }
            function getParameter(paraStr, url)
            {
                var result = "";
                //获取URL中全部参数列表数据
                var str = "&" + url.split("?")[1];
                var paraName = paraStr + "=";
                //判断要获取的参数是否存在
                if (str.indexOf("&" + paraName) != -1)
                {
                    //如果要获取的参数到结尾是否还包含“&”
                    if (str.substring(str.indexOf(paraName), str.length).indexOf("&") != -1)
                    {
                        //得到要获取的参数到结尾的字符串
                        var TmpStr = str.substring(str.indexOf(paraName), str.length);
                        //截取从参数开始到最近的“&”出现位置间的字符
                        result = TmpStr.substr(TmpStr.indexOf(paraName), TmpStr.indexOf("&") - TmpStr.indexOf(paraName)).split("=")[1];
                    }
                    else
                    {
                        result = str.substring(str.indexOf(paraName), str.length).split("=")[1];
                    }
                }
                else
                {
                    result = "null";
                }
                return (result.replace("&", ""));
            }

            function Snow() {

                var type = getParameter("type", thisURL);
                var size = getParameter("size", thisURL);
                var num = getParameter("num", thisURL);
                //document.write( "<tr><td valign=top>r: </td><td>"+type+"</td></tr>" ); 
                //document.write( "<tr><td valign=top>r: </td><td>"+size+"</td></tr>" ); 
                //document.write( "<tr><td valign=top>r: </td><td>"+num+"</td></tr>" ); 
                if (type == "null") {
                    type = "images/snow/";
                    if (size == "null")
                        size = 5;
                }
                if (type == "big") {
                    type = "images/big-24/";
                    if (size == "null")
                        size = 12;
                }
                if (type == "ice") {
                    type = "images/ice-24/";
                    if (size == "null")
                        size = 12;
                }
                if (type == "medium") {
                    type = "images/medium-10/";
                    if (size == "null")
                        size = 10;
                }
                if (type == "presents") {
                    type = "images/presents-32/";
                    if (size == "null")
                        size = 16;
                }
                if (type == "small") {
                    type = "images/small-02/";
                    if (size == "null")
                        size = 2;
                }
                if (type == "snow") {
                    type = "images/snow/";
                    if (size == "null")
                        size = 5;
                }
                if (num == "null") {
                    num = 100;
                }

                //3 parameter 
                //first the type of snow 
                //seconde the size
                //third the num
                createSnow(type, size, num);
            }


            Snow();