送上段模拟圣诞节下雪的javascript 代码

<script type="text/javascript"> // Set the number of snowflakes (more than 30 - 40 not recommended) var snowmax=50 // Set the colors for the snow. Add as many colors as you like var snowcolor=new Array("#aaaacc","#ddddff","#ccccdd","#f3f3f3","#f0ffff","#bbf7f9") // Set the fonts, that create the snowflakes. Add as many fonts as you like var snowtype=new Array("Times","Arial","Times","Verdana") // Set the letter that creates your snowflake (recommended: * ) var snowletter="*" // Set the speed of sinking (recommended values range from 0.3 to 2) var sinkspeed=0.6 // Set the maximum-size of your snowflakes var snowmaxsize=30 // Set the minimal-size of your snowflakes var snowminsize=8 // Set the snowing-zone // Set 1 for all-over-snowing, set 2 for left-side-snowing // Set 3 for center-snowing, set 4 for right-side-snowing var snowingzone=1 /////////////////////////////////////////////////////////////////////////// var snow=new Array() var marginbottom var marginright var timer var i_snow=0 var x_mv=new Array(); var crds=new Array(); var lftrght=new Array(); var browserinfos=navigator.userAgent var ie5=document.all&&document.getElementById&&!browserinfos.match(/Opera/) var ns6=document.getElementById&&!document.all var opera=browserinfos.match(/Opera/) var browserok=ie5||ns6||opera   function randommaker(range) { rand=Math.floor(range*Math.random()) return rand }   function initsnow() { if (ie5 || opera) { marginbottom = document.body.scrollHeight marginright = document.body.clientWidth-15 } else if (ns6) { marginbottom = document.body.scrollHeight marginright = window.innerWidth-15 } var snowsizerange=snowmaxsize-snowminsize for (i=0;i<=snowmax;i++) { crds[i] = 0; lftrght[i] = Math.random()*15; x_mv[i] = 0.03 + Math.random()/10; snow[i]=document.getElementById("s"+i) snow[i].style.fontFamily=snowtype[randommaker(snowtype.length)] snow[i].size=randommaker(snowsizerange)+snowminsize snow[i].style.fontSize=snow[i].size+'px'; snow[i].style.color=snowcolor[randommaker(snowcolor.length)] snow[i].style.zIndex=1000 snow[i].sink=sinkspeed*snow[i].size/5 if (snowingzone==1) {snow[i].posx=randommaker(marginright-snow[i].size)} if (snowingzone==2) {snow[i].posx=randommaker(marginright/2-snow[i].size)} if (snowingzone==3) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/4} if (snowingzone==4) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/2} snow[i].posy=randommaker(2*marginbottom-marginbottom-2*snow[i].size) snow[i].style.left=snow[i].posx+'px'; snow[i].style.top=snow[i].posy+'px'; } movesnow() }   function movesnow() { for (i=0;i<=snowmax;i++) { crds[i] += x_mv[i]; snow[i].posy+=snow[i].sink snow[i].style.left=snow[i].posx+lftrght[i]*Math.sin(crds[i])+'px'; snow[i].style.top=snow[i].posy+'px';   if (snow[i].posy>=marginbottom-2*snow[i].size || parseInt(snow[i].style.left)>(marginright-3*lftrght[i])){ if (snowingzone==1) {snow[i].posx=randommaker(marginright-snow[i].size)} if (snowingzone==2) {snow[i].posx=randommaker(marginright/2-snow[i].size)} if (snowingzone==3) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/4} if (snowingzone==4) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/2} snow[i].posy=0 } } var timer=setTimeout("movesnow()",50) }   for (i=0;i<=snowmax;i++) { document.write("<span id='s"+i+"' style='position:absolute;top:-"+snowmaxsize+"'>"+snowletter+"</span>") } if (browserok) { window.onload=initsnow } </script>