JS实现LOGO像雪花一样落下的特效

2012-11-08 来源：网络
【实例名称】
JS实现LOGO像雪花一样落下的特效
【实例描述】
在页面中可以经常看到一些像雪花一样落下的文本、广告、图片等。本例将以具体实例演示如何设计像雪花一样落下的LOGO。
【实例代码】
<HTML><HEAD><TITLE>LOGO从上落下-学无忧（www.xue51.com）</title>
<SCRIPT language=JavaScript>
//窗口改变时重新加载页面  -Netscape的浏览器
function MM_reloadPage(init) {  
  if (init==true) with (navigator) {if 
((appName=="Netscape")&&(parseInt(appVersion)==4)) {
    document.MM_pgW=innerWidth; 
document.MM_pgH=innerHeight; onresize=MM_reloadPage; }}
  else if (innerWidth!=document.MM_pgW || 
innerHeight!=document.MM_pgH) location.reload();
}
MM_reloadPage(true);
//窗口改变时重新加载页面  -IE浏览器
function MM_preloadImages() { 
  var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
    var i,j=d.MM_p.length,a=MM_preloadImages.arguments; 
for(i=0; i<a.length; i++)
    if (a[i].indexOf("#")!=0){ d.MM_p[j]=new Image; 
d.MM_p[j++].src=a[i];}}
  sjLayer.style.visibility='hidden';
  eslayer.style.visibility='hidden';
}
function MM_swapImgRestore() { 
  var i,x,a=document.MM_sr; 
for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++) x.src=x.oSrc;
}
function MM_findObj(n, d) {
  var p,i,x;  if(!d) d=document; 
if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; 
n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; 
for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) 
x=MM_findObj(n,d.layers[i].document); return x;
}
function MM_showHideLayers() {
  var i,p,v,obj,args=MM_showHideLayers.arguments;
  for (i=0; i<(args.length-2); i+=3) 
if ((obj=MM_findObj(args[i]))!=null) { v=args[i+2];
    if (obj.style) { obj=obj.style; 
v=(v=='show')?'visible':(v='hide')?'hidden':v; }
    obj.visibility=v; }
}
</SCRIPT>
</HEAD>
<BODY  >
<SCRIPT language=JavaScript>
//判断浏览器
var ns4up = (document.layers) ? 1 : 0;  
var ie4up = (document.all) ? 1 : 0;
var no = 3;                            
 // 显示的图像数量
var speed = 20;                        
 // 图像移动的速度
var snowflake ="LOGO1.gif";     
 //图像地址
var filen = http://www.baidu.com 
 // 单击图像时的链接
var dx, xp, yp;                        
var am, stx, sty;                      
var i, doc_width = 400, doc_height = 600;
if (ns4up) {
doc_width = self.innerWidth;
doc_height = self.innerHeight;
} else if (ie4up) {
doc_width = document.body.clientWidth;
doc_height = document.body.clientHeight;
}
dx = new Array();
xp = new Array();
yp = new Array();
am = new Array();
stx = new Array();
sty = new Array();
for (i = 0; i < no; ++ i) 
{  
dx[i] = 0;                             
// set coordinate variables
xp[i] = Math.random()*(doc_width-50);  
// set position variables
yp[i] = Math.random()*doc_height;
am[i] = Math.random()*20;              
// set amplitude variables
stx[i] = 0.02 + Math.random()/10;      
// set step variables
sty[i] = 0.7 + Math.random();          
// set step variables
if (ns4up) {                           
// set layers
if (i == 0) {
document.write("<html><title>-学无忧（www.xue51.com）
</title><body>");
document.write("<layer name=\"dot"+ i +"\" left=\"15\" ");
document.write("top=\"15\" visibility=\"show\"><A href=\"" + 
filen + "\" target=\"_blank\"><img src=\"");
document.write(snowflake + "\" border=\"0\"></layer>");
document.write("</body></html>");
} else {
document.write("<html><title>-学无忧（www.xue51.com）</title><body>");
document.write("<layer name=\"dot"+ i +"\" left=\"15\" ");
document.write("top=\"15\" visibility=\"show\"><A href=\"" + 
filen + "\" target=\"_blank\"><img src=\"");
document.write(snowflake + "\" border=\"0\"></layer>");
document.write("</body></html>");
}
} else if (ie4up) {
if (i == 0) {
document.write("<html><title>-学无忧（www.xue51.com）
</title><body>");
document.write("<div id=\"dot"+ i +"\" style=\"POSITION: ");
document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
document.write("visible; TOP: 15px; LEFT: 15px;\">
<a href=\""+filen+"\" target=\"_blank\"><img src=\"");
document.write(snowflake + "\" border=\"0\"></div>");
document.write("</body></html>");
} else {
document.write("<html><title>-学无忧（www.xue51.com）</title><body>");
document.write("<div id=\"dot"+ i +"\" style=\"POSITION: ");
document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
document.write("visible; TOP: 15px; LEFT: 15px;\"><a 
href=\""+filen+"\" target=\"_blank\"><img src=\"");
document.write(snowflake + "\" border=\"0\"></div>");
document.write("</body></html>");
}
}
}
//实现Netscape浏览器中动画效果的方法
function snowNS() { 
    for (i = 0; i < no; ++ i) 
    { 
        yp[i] += sty[i];
        if (yp[i] > doc_height-50) {
        xp[i] = Math.random()*(doc_width-am[i]-30);
        yp[i] = 0;
        stx[i] = 0.02 + Math.random()/10;
        sty[i] = 0.7 + Math.random();
        doc_width = self.innerWidth;
        doc_height = self.innerHeight;
        }
dx[i] += stx[i];
//指定图像的显示位置：x和y坐标
document.layers["dot"+i].top = yp[i];
document.layers["dot"+i].left = xp[i] + am[i]*Math.sin(dx[i]);
    }
    setTimeout("snowNS()", speed);
}
//实现IE浏览器中动画效果的方法
function snowIE() 
{  
    //判断图像的数量
    for (i = 0; i < no; ++ i) {  
        yp[i] += sty[i];
        if (yp[i] > doc_height-50) {
        xp[i] = Math.random()*(doc_width-am[i]-30);
        yp[i] = 0;
        stx[i] = 0.02 + Math.random()/10;
        sty[i] = 0.7 + Math.random();
        //重新获取文档的高度和宽度
        doc_width = document.body.clientWidth;
        doc_height = document.body.clientHeight;
        }
 dx[i] += stx[i];
//指定图像的显示位置：x和y坐标
document.all["dot"+i].style.pixelTop = yp[i];
document.all["dot"+i].style.pixelLeft = xp[i] + am[i]*Math.sin(dx[i]);
    }
    setTimeout("snowIE()", speed);  
//根据速度循环执行动画方法
}
//判断浏览器类型，并调用不同的动画方法
if (ns4up) {
 snowNS();
} else if (ie4up) {
 snowIE();
}
</SCRIPT>
</TABLE>
</BODY></HTML>
【运行效果】
LOGO像雪花一样落下运行效果