<p><textarea id=t1 cols=95 rows=20>
<html>
<head>
<title>雪</title>
</head>
<body bgcolor=#000000 >
<h1 align="center">
<font color="#FFFFFF">S N O W</font>
<script language="JavaScript">
<!--
var no = 15;
var ns4up = (document.layers) ? 1 : 0;
var ie4up = (document.all) ? 1 : 0;
var s, x, y, sn, cs;
var a, r, cx, cy;
var i, doc_width = 800, 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;
}
x = new Array();
y = new Array();
r = new Array();
cx = new Array();
cy = new Array();
s = 10;
for (i = 0; i < no; i++)
{
initsnow();
if (ns4up)
{
document.write("<layer name=\"dot"+ i +"\" left=\"1\" ");
document.write("top=\"1\" visibility=\"show\"><font color=\"white\">");
document.write("*</font></layer>");
}
else if (ie4up)
{
document.write("<div id=\"dot"+ i +"\" style=\"POSITION: ");
document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
document.write("visible; TOP: 15px; LEFT: 15px;\"><font color=\"white\">");
document.write("*</font></div>");
}
}
function initsnow()
{
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 makesnow()
{
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];
}
function snowdropNS()
{
for (i = 0; i < no; i++)
{
r[i] += s;
x[i] = r[i] * sn + cx[i];
y[i] = r[i] * cs + cy[i];
if ((x[i] <= 1) || (x[i] >= doc_width) || (y[i] >= doc_height))
{
makesnow();
doc_width = self.innerWidth;
doc_height = self.innerHeight;
}
document.layers["dot"+i].top = y[i];
document.layers["dot"+i].left = x[i];
}
setTimeout("snowdropNS()", 100);
}
function snowdropIE()
{
for (i = 0; i < no; ++ i)
{
r[i] += s;
x[i] = r[i] * sn + cx[i];
y[i] = r[i] * cs + cy[i];
if ((x[i] <= 1) || (x[i] >= doc_width) || (y[i] >= doc_height))
{
makesnow();
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("snowdropIE()", 100);
}
if (ns4up)
{
snowdropNS();
}
else
if (ie4up)
{
snowdropIE();
}
-->
</script>
</body>
</html>
</textarea><BR>
看看这段程序，程序中的a变量可以决定雪花的飘落方向~
为什么？？不懂~请教大家了~~~
完全是算法的问题，如果看不懂就...