[Javascript] Tuyết rơi

var snowStorm = null;

function SnowStorm() {

// PROPERTIES
// ------------------

var imagePath = 'http://img.forum.zing.vn/images/snow/'; // relative path to snow images (including trailing slash)
var flakesMax = 128;
var flakesMaxActive = 64;
var vMaxX = 8;
var vMaxY = 4;
var usePNG = true;
var flakeBottom = null; // Integer for fixed bottom, 0 or null for "full-screen" snow effect
var snowStick = true;
var snowCollect = false;
var targetElement = null; // element which snow will be appended to (document body if undefined)
var followMouse = true;
var flakeTypes = 6;
var flakeWidth = 5;
var flakeHeight = 5;

// ------------------

var zIndex = 0; // CSS stacking order applied to each snowflake
var flakeLeftOffset = 0; // amount to subtract from edges of container
var flakeRightOffset = 0; // amount to subtract from edges of container

// --- End of user section ---

var addEvent = function(o,evtName,evtHandler) {
typeof(attachEvent)=='undefined'?o.addEventListener(evtName,evtHandler,false):o.attachEvent('on'+evtName,evtHandler);
}

var removeEvent = function(o,evtName,evtHandler) {
typeof(attachEvent)=='undefined'?o.removeEventListener(evtName,evtHandler,false):o.detachEvent('on'+evtName,evtHandler);
}

var classContains = function(o,cStr) {
return (typeof(o.className)!='undefined'?o.className.indexOf(cStr)+1:false);
}

var s = this;
var storm = this;
this.timers = [];
this.flakes = [];
this.disabled = false;
this.terrain = [];
this.active = false;

var isIE = navigator.userAgent.match(/msie/i);
var isIE6 = navigator.userAgent.match(/msie 6/i);
var isOldIE = (isIE && (isIE6 || navigator.userAgent.match(/msie 5/i)));
var isWin9X = navigator.appVersion.match(/windows 98/i);
var isiPhone = navigator.userAgent.match(/iphone/i);
var isOpera = navigator.userAgent.match(/opera/i);
if (isOpera) isIE = false; // Opera (which may be sneaky, pretending to be IE by default)
var screenX = null;
var screenX2 = null;
var screenY = null;
var scrollY = null;
var vRndX = null;
var vRndY = null;
var windOffset = 1;
var windMultiplier = 2;
var pngSupported = (!isIE || (isIE && !isIE6 && !isOldIE)); // IE <7 doesn't do PNG nicely without crap filters
var docFrag = document.createDocumentFragment();
this.oControl = null; // toggle element
if (flakeLeftOffset == null) flakeLeftOffset = 0;
if (flakeRightOffset == null) flakeRightOffset = 0;

function rnd(n,min) {
if (isNaN(min)) min = 0;
return (Math.random()*n)+min;
}

this.randomizeWind = function() {
vRndX = plusMinus(rnd(vMaxX,0.2));
vRndY = rnd(vMaxY,0.2);
if (this.flakes) {
for (var i=0; i<this.flakes.length; i++) {
if (this.flakes[i].active) this.flakes[i].setVelocities();
}
}
}

function plusMinus(n) {
return (parseInt(rnd(2))==1?n*-1:n);
}

this.scrollHandler = function() {
// "attach" snowflakes to bottom of window if no absolute bottom value was given
scrollY = (flakeBottom?0:parseInt(window.scrollY||document.documentElement.scrollTop||document.body.scrollTop));
if (isNaN(scrollY)) scrollY = 0; // Netscape 6 scroll fix
if (!flakeBottom && s.flakes) {
for (var i=0; i<s.flakes.length; i++) {
if (s.flakes[i].active == 0) s.flakes[i].stick();
}
}
}

this.resizeHandler = function() {
if (window.innerWidth || window.innerHeight) {
screenX = window.innerWidth-(!isIE?16:2)-flakeRightOffset;
screenY = (flakeBottom?flakeBottom:window.innerHeight);
} else {
screenX = (document.documentElement.clientWidth||document.body.clientWidth||document.body.scrollWidth)-(!isIE?8:0)-flakeRightOffset;
screenY = flakeBottom?flakeBottom:(document.documentElement.clientHeight||document.body.clientHeight||document.body.scrollHeight);
}
screenX2 = parseInt(screenX/2);
}

this.resizeHandlerAlt = function() {
screenX = targetElement.offsetLeft+targetElement.offsetWidth-flakeRightOffset;
screenY = flakeBottom?flakeBottom:targetElement.offsetTop+targetElement.offsetHeight;
screenX2 = parseInt(screenX/2);
}

this.freeze = function() {
// pause animation
if (!s.disabled) {
s.disabled = 1;
} else {
return false;
}
for (var i=0; i<s.timers.length; i++) {
clearInterval(s.timers[i]);
}
}

this.resume = function() {
if (s.disabled) {
s.disabled = 0;
} else {
return false;
}
s.timerInit();
}

this.toggleSnow = function() {
if (!s.flakes.length) {
// first run
s.start();
s.setControlActive(true);
} else {
s.active = !s.active;
if (s.active) {
s.show();
s.resume();
s.setControlActive(true);
} else {
s.stop();
s.freeze();
s.setControlActive(false);
}
}
}

this.setControlActive = function(bActive) {
// Y.D[(bActive?'addClass':'removeClass')](s.oControl,'active');
}

this.stop = function() {
this.freeze();
for (var i=this.flakes.length; i--;) {
this.flakes[i].o.style.display = 'none';
}
removeEvent(window,'scroll',s.scrollHandler);
removeEvent(window,'resize',s.resizeHandler);
if (!isIE) {
removeEvent(window,'blur',s.freeze);
removeEvent(window,'focus',s.resume);
}
// removeEventHandler(window,'resize',this.resizeHandler,false);
}

this.show = function() {
for (var i=this.flakes.length; i--;) {
this.flakes[i].o.style.display = 'block';
}
}

this.SnowFlake = function(parent,type,x,y) {
var s = this;
var storm = parent;
this.type = type;
this.x = x||parseInt(rnd(screenX-20));
this.y = (!isNaN(y)?y:-rnd(screenY)-12);
this.vX = null;
this.vY = null;
this.vAmpTypes = [2.0,1.0,1.25,1.0,1.5,1.75]; // "amplification" for vX/vY (based on flake size/type)
this.vAmp = this.vAmpTypes[this.type];

this.active = 1;
this.o = document.createElement('img');
this.o.style.position = 'absolute';
this.o.style.width = flakeWidth+'px';
this.o.style.height = flakeHeight+'px';
this.o.style.fontSize = '1px'; // so IE keeps proper size
this.o.style.zIndex = zIndex;
this.o.src = imagePath+this.type+(pngSupported && usePNG?'.png':'.gif');
docFrag.appendChild(this.o);

this.refresh = function() {
s.o.style.left = s.x+'px';
s.o.style.top = s.y+'px';
}

this.stick = function() {
if (isIE6 || isiPhone || (targetElement != document.documentElement && targetElement != document.body)) {
s.o.style.top = (screenY+scrollY-flakeHeight-storm.terrain[Math.floor(s.x)])+'px';
} else {
s.o.style.display = 'none';
s.o.style.top = 'auto';
s.o.style.bottom = '0px';
s.o.style.position = 'fixed';
s.o.style.display = 'block';
}
}

this.vCheck = function() {
if (s.vX>=0 && s.vX<0.2) {
s.vX = 0.2;
} else if (s.vX<0 && s.vX>-0.2) {
s.vX = -0.2;
}
if (s.vY>=0 && s.vY<0.2) {
s.vY = 0.2;
}
}

this.move = function() {
s.x += s.vX*windOffset;
s.y += (s.vY*s.vAmp);
s.refresh();
if (s.vX && screenX-s.x<flakeWidth+(s.vX*windOffset)) { // X-axis scroll check
s.x = 0;
} else if ((s.vX<0 || windOffset<0)&& s.x-flakeLeftOffset<0-flakeWidth) {
s.x = screenX-flakeWidth; // flakeWidth;
}
var yDiff = screenY+scrollY-s.y-storm.terrain[Math.floor(s.x)];
if (yDiff<flakeHeight) {
s.active = 0;
if (snowCollect && snowStick) {
var height = [0.75,1.5,0.75];
for (var i=0; i<2; i++) {
storm.terrain[Math.floor(s.x)+i+2] += height[i];
}
}
s.o.style.left = (s.x/screenX*100)+'%'; // set "relative" left (change with resize)
if (!flakeBottom) {
if (snowStick) {
s.stick();
} else {
s.recycle();
}
}
}
}

this.animate = function() {
// main animation loop
// move, check status, die etc.
s.move();
}

this.setVelocities = function() {
s.vX = vRndX+rnd(vMaxX*0.12,0.1);
s.vY = vRndY+rnd(vMaxY*0.12,0.1);
}

this.recycle = function() {
s.o.style.display = 'none';
s.o.style.position = 'absolute';
s.o.style.bottom = 'auto';
s.setVelocities();
s.vCheck();
s.x = parseInt(rnd(screenX-flakeWidth-20));
s.y = parseInt(rnd(screenY)*-1)-flakeHeight;
s.o.style.left = s.x+'px';
s.o.style.top = s.y+'px';
s.o.style.display = 'block';
s.active = 1;
}

this.recycle(); // set up x/y coords etc.
this.refresh();

}

this.snow = function() {
var active = 0;
var used = 0;
var waiting = 0;
for (var i=s.flakes.length; i--;) {
if (s.flakes[i].active == 1) {
s.flakes[i].move();
active++;
} else if (s.flakes[i].active == 0) {
used++;
} else {
waiting++;
}
}
if (snowCollect && !waiting) { // !active && !waiting
// create another batch of snow
s.createSnow(flakesMaxActive,true);
}
if (active<flakesMaxActive) {
with (s.flakes[parseInt(rnd(s.flakes.length))]) {
if (!snowCollect && active == 0) {
recycle();
} else if (active == -1) {
active = 1;
}
}
}
}

this.mouseMove = function(e) {
if (!followMouse) return true;
var x = parseInt(e.clientX);
if (x<screenX2) {
windOffset = -windMultiplier+(x/screenX2*windMultiplier);
} else {
x -= screenX2;
windOffset = (x/screenX2)*windMultiplier;
}
}

this.createSnow = function(limit,allowInactive) {
for (var i=0; i<limit; i++) {
s.flakes[s.flakes.length] = new s.SnowFlake(s,parseInt(rnd(flakeTypes)));
if (allowInactive || i>flakesMaxActive) s.flakes[s.flakes.length-1].active = -1;
}
targetElement.appendChild(docFrag);
}

this.timerInit = function() {
s.timers = (!isWin9X?[setInterval(s.snow,20)]:[setInterval(s.snow,75),setInterval(s.snow,25)]);
}

this.init = function() {
for (var i=0; i<2048; i++) {
s.terrain[i] = 0;
}
s.randomizeWind();
s.createSnow(snowCollect?flakesMaxActive:flakesMaxActive*2); // create initial batch
addEvent(window,'resize',s.resizeHandler);
addEvent(window,'scroll',s.scrollHandler);
if (!isIE) {
addEvent(window,'blur',s.freeze);
addEvent(window,'focus',s.resume);
}
s.resizeHandler();
s.scrollHandler();
if (followMouse) {
addEvent(document,'mousemove',s.mouseMove);
}
s.timerInit();
}

var didInit = false;

this.start = function(bFromOnLoad) {
if (!didInit) {
didInit = true;
} else if (bFromOnLoad) {
// already loaded and running
return true;
}
if (typeof targetElement == 'string') {
targetElement = document.getElementById(targetElement);
if (!targetElement) throw new Error('Snowstorm: Unable to get targetElement');
}
if (!targetElement) {
targetElement = (!isIE?(document.documentElement?document.documentElement:document.body):document.body);
}
if (targetElement != document.documentElement && targetElement != document.body) s.resizeHandler = s.resizeHandlerAlt; // re-map handler to get element instead of screen dimensions
s.resizeHandler(); // get bounding box elements
if (screenX && screenY && !s.disabled) {
s.init();
s.active = true;
}
}

if (document.addEventListener) {
// safari 3.0.4 doesn't do DOMContentLoaded, maybe others - use a fallback to be safe.
document.addEventListener('DOMContentLoaded',function(){s.start(true)},false);
window.addEventListener('load',function(){s.start(true)},false);
} else {
addEvent(window,'load',function(){s.start(true)});
}

}



snowStorm = new SnowStorm();