本文實例講述了JavaScript生成的動態下雨背景效果實現方法。分享給大家供大家參考。具體實現方法如下：
複製代碼代碼如下:<HTML>
<HEAD>
<TITLE>JavaScript生成的動態下雨背景效果</TITLE>
</HEAD>
<BODY bgcolor="#fef4d2" >
<center>
<script language=JavaScript>
<!-- [Step1]: 在此能夠設置雨滴的多少-->
var rainsize = 40;
<!-- [Step2]: 這裡可以更改下雨的速度，數值大速度慢-->
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>
希望本文所述對大家的javascript程序設計有所幫助。