通过JavaScript实现下雪效果的方法
代码1：
<title>Happy New Year</title>
<body bgcolor="#ff3300" leftmargin="0" topmargin="0" onLoad="snow()" AAAD98>
<script language="JavaScript">
<!--
N = 100;
Y = new Array();
X = new Array();
S = new Array();
A = new Array();
B = new Array();
M = new Array();
V = (document.layers)?1:0;
iH=(document.layers)?window.innerHeight:window.document.body.clientHeight;
iW=(document.layers)?window.innerWidth:window.document.body.clientWidth;
for (i=0; i < N; i++){
Y[i]=Math.round(Math.random()*iH);
X[i]=Math.round(Math.random()*iW);
S[i]=Math.round(Math.random()*5+2);
A[i]=0;
B[i]=Math.random()*0.1+0.1;
M[i]=Math.round(Math.random()*1+1);
}
if (V){
for (i = 0; i < N; i++)
{document.write("<LAYER NAME='sn"+i+"' LEFT=0 TOP=0 BGCOLOR='#ffffff' CLIP='0,0,"+M[i]+","+M[i]+"'></LAYER>")}
}
else{
document.write('<div style="position:absolute;top:0px;left:0px">');
document.write('<div style="position:relative">');
for (i = 0; i < N; i++)
{document.write('<div id="si" style="position:absolute;top:0;left:0;width:'+M[i]+';height:'+M[i]+';background:#ffffff;font-size:'+M[i]+'"></div>')}
document.write('</div></div>');
}
function snow(){
var H=(document.layers)?window.innerHeight:window.document.body.clientHeight;
var W=(document.layers)?window.innerWidth:window.document.body.clientWidth;
var T=(document.layers)?window.pageYOffset:document.body.scrollTop;
var L=(document.layers)?window.pageXOffset:document.body.scrollLeft;
for (i=0; i < N; i++){
sy=S[i]*Math.sin(90*Math.PI/180);
sx=S[i]*Math.cos(A[i]);
Y[i]+=sy;
X[i]+=sx;
if (Y[i] > H){
Y[i]=-10;
X[i]=Math.round(Math.random()*W);
M[i]=Math.round(Math.random()*1+1);
S[i]=Math.round(Math.random()*5+2);
}
if (V){document.layers['sn'+i].left=X[i];document.layers['sn'+i].top=Y[i]+T}
else{si[i].style.pixelLeft=X[i];si[i].style.pixelTop=Y[i]+T}
A[i]+=B[i];
}
setTimeout('snow()',20);
}
//-->
</script>
代码2：
<body bgcolor=#ee3300>
<style>
.drop { position: absolute; width: 3; filter: flipV(), flipH(); font-size: 40; color: #ffffff }
</style>
<script language="javascript">
snow = false; // false-rain; true-snow
snowsym = " * " file://These are the symbols for each
rainsym = " * " file://You can put images here.
howmany = 20 file://How many drops/snowflakes?
/**************Do not need to change anything below***********/
if(snow){sym = snowsym; speed=1; angle=10; drops=howmany}
else{sym = rainsym; speed=30; drops=howmany; angle=6}
movex = -speed/angle; movey = speed; count = 0;
function moverain(){
for(move = 0; move < drops; move++){
xx[move]+=movex; yy[move]+=mv[move];
hmm = Math.round(Math.random()*1);
if(xx[move] < 0){xx[move] = maxx+10;}
if(yy[move] > maxy){yy[move] = 10;}
drop[move].left = xx[move]
drop[move].top = yy[move]+document.body.scrollTop;
}setTimeout('moverain()','1')}
</script>
<script language="javascript">
if (document.all){
drop = new Array(); xx = new Array(); yy = new Array(); mv = new Array()
ly = "document.all[/'"; st = "/'].style"
for(make = 0; make < drops; make++){
document.write('<div id="drop'+make+'" class=drop>'+sym+'</div>');
drop[make] = eval(ly+'drop'+make+st);
maxx = document.body.clientWidth-40
maxy = document.body.clientHeight-40
xx[make] = Math.random()*maxx;
yy[make] = -100-Math.random()*maxy;
drop[make].left = xx[make]
drop[make].top = yy[make]
mv[make] = (Math.random()*5)+speed/16;
drop[make].fontSize = (Math.random()*10)+20;
if(snow){col = 'white'}else{col = 'white'}
drop[make].color = col;
}
window.onload=moverain
}
</script>
</body>
代码3：
<body bgcolor=#ee3300>
<script LANGUAGE="JavaScript1.2">
<!--
var no = 25;
var speed = 10;
var snowflake = "http://www.cnbruce.com/blog/uploadimg/2004122215384750532.gif";
var ns4up = (document.layers) ? 1 : 0;
var ie4up = (document.all) ? 1 : 0;
var dx, xp, yp;
var am, stx, sty;
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;
}
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;
xp[i] = Math.random()*(doc_width-50);
yp[i] = Math.random()*doc_height;
am[i] = Math.random()*20;
stx[i] = 0.02 + Math.random()/10;
sty[i] = 0.7 + Math.random();
if (ns4up) {
if (i == 0) {
document.write("<layer name=/"dot"+ i +"/" left=/"15/" ");
document.write("top=/"15/" visibility=/"show/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></layer>");
} else {
document.write("<layer name=/"dot"+ i +"/" left=/"15/" ");
document.write("top=/"15/" visibility=/"show/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></layer>");
}
} else if (ie4up) {
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;/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></div>");
} else {
document.write("<div id=/"dot"+ i +"/" style=/"POSITION: ");
document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
document.write("visible; TOP: 15px; LEFT: 15px;/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></div>");
}
}
}
function snowNS() { // Netscape main animation function
for (i = 0; i < no; ++ i) { // iterate for every dot
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];
document.layers["dot"+i].top = yp[i];
document.layers["dot"+i].left = xp[i] + am[i]*Math.sin(dx[i]);
}
setTimeout("snowNS()", speed);
}
function snowIE() { // IE main animation function
for (i = 0; i < no; ++ i) { // iterate for every dot
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 = document.body.clientWidth;
doc_height = document.body.clientHeight;
}
dx[i] += stx[i];
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);
}
if (ns4up) {
snowNS();
} else if (ie4up) {
snowIE();
}
//-->
</script>
</body>
代码4：
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