JavaScript 实现动态下雨背景效果

JavaScript 动态下雨背景效果实现

本文分享一种利用 JavaScript 创建动态下雨背景效果的实现方案，供开发者参考。核心思路是通过脚本控制页面元素的位置变化，模拟雨滴下落过程。

<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。