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JavaScript生成的动态下雨背景效果实现方法

2015-02-25 00:00 2321 查看
本文实例讲述了JavaScript生成的动态下雨背景效果实现方法。分享给大家供大家参考。具体实现方法如下：

<HTML>

<HEAD>

<TITLE>JavaScript生成的动态下雨背景效果</TITLE>

</HEAD>

<BODY bgcolor="#fef4d2" >

<center>

<script language=JavaScript>

<!-- [Step1]: 在此能够设置雨滴的多少 -->

var rainsize = 40;

<!-- [Step2]: 这里可以更改下雨的速度，数值大速度慢 -->

var speed = 10;

var x = new Array();

var y = new Array();

var r = new Array();

var cx = new Array();

var cy = new Array();

var doc_width = document.body.clientWidth;

var doc_height = document.body.clientHeight;
for(i=0; i<rainsize; ++i) { 

  initRain();

  if (i == 0) {

    document.write("<div id=\"dot"+ i +"\" style=\"POSITION: ");

    document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");

    document.write("visible; TOP: 15px; LEFT: 15px;\"><font color=\"blue\">");

    document.write(",</font></div>"); }

  else {

    document.write("<div id=\"dot"+ i +"\" style=\"POSITION: ");

    document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");

    document.write("visible; TOP: 15px; LEFT: 15px;\"><font color=\"blue\">");

    document.write(",.</font></div>");  }

}
function initRain() {

  a = 6;

  r[i] = 1;

  sn = Math.sin(a);

  cs = Math.cos(a);

  cx[i] = Math.random() * doc_width + 1;

  cy[i] = Math.random() * doc_height + 1;

  x[i] = r[i] * sn + cx[i];

  y[i] = cy[i];

}
function raindropIE() {

  for (i = 0; i < rainsize; ++ i) {

     updateRain();

     if ((x[i] <= 1) || (x[i] >= (doc_width - 20)) || (y[i] >= (doc_height - 20))) {

         makeRain();

         doc_width = document.body.clientWidth;

         doc_height = document.body.clientHeight; }

     document.all["dot"+i].style.pixelTop = y[i];

     document.all["dot"+i].style.pixelLeft = x[i]; }

  setTimeout("raindropIE()", speed); 

}

function updateRain() {

  r[i] += 10;

  x[i] = r[i] * sn + cx[i];

  y[i] = r[i] * cs + cy[i];

}

function makeRain() {

  r[i] = 1;

  cx[i] = Math.random() * doc_width + 1;

  cy[i] = 1;

  x[i] = r[i] * sn + cx[i];

  y[i] = r[i] * cs + cy[i];

}

raindropIE();

</script> 

</BODY>

</HTML>

希望本文所述对大家的javascript程序设计有所帮助。
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标签：  动态下雨 背景效果
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