SnowFall

/** @license
* DHTML Snowstorm! JavaScript-based snow for web pages
* Making it snow on the internets since 2003. You're welcome.
* -----------------------------------------------------------
* Version 1.44.20131215 (Previous rev: 1.44.20131208)
* Copyright (c) 2007, Scott Schiller. All rights reserved.
* Code provided under the BSD License
* http://schillmania.com/projects/snowstorm/license.txt
*/
/*jslint nomen: true, plusplus: true, sloppy: true, vars: true, white: true */
/*global window, document, navigator, clearInterval, setInterval */
var snowStorm = (function(window, document) {
// --- common properties ---
this.autoStart = true; // Whether the snow should start automatically or not.
this.excludeMobile = true; // Snow is likely to be bad news for mobile phones' CPUs (and batteries.) Enable at your own risk.
this.flakesMax = 128; // Limit total amount of snow made (falling + sticking)
this.flakesMaxActive = 64; // Limit amount of snow falling at once (less = lower CPU use)
this.animationInterval = 33; // Theoretical "miliseconds per frame" measurement. 20 = fast + smooth, but high CPU use. 50 = more conservative, but slower
this.useGPU = true; // Enable transform-based hardware acceleration, reduce CPU load.
this.className = null; // CSS class name for further customization on snow elements
this.excludeMobile = true; // Snow is likely to be bad news for mobile phones' CPUs (and batteries.) By default, be nice.
this.flakeBottom = null; // Integer for Y axis snow limit, 0 or null for "full-screen" snow effect
this.followMouse = false; // Snow movement can respond to the user's mouse
this.snowColor = '#99ccff'; // Don't eat (or use?) yellow snow.
this.snowCharacter = '•'; // • = bullet, · is square on some systems etc.
this.snowStick = true; // Whether or not snow should "stick" at the bottom. When off, will never collect.
this.targetElement = null; // element which snow will be appended to (null = document.body) - can be an element ID eg. 'myDiv', or a DOM node reference
this.useMeltEffect = true; // When recycling fallen snow (or rarely, when falling), have it "melt" and fade out if browser supports it
this.useTwinkleEffect = false; // Allow snow to randomly "flicker" in and out of view while falling
this.usePositionFixed = false; // true = snow does not shift vertically when scrolling. May increase CPU load, disabled by default - if enabled, used only where supported
this.usePixelPosition = false; // Whether to use pixel values for snow top/left vs. percentages. Auto-enabled if body is position:relative or targetElement is specified.
// --- less-used bits ---
this.freezeOnBlur = true; // Only snow when the window is in focus (foreground.) Saves CPU.
this.flakeLeftOffset = 0; // Left margin/gutter space on edge of container (eg. browser window.) Bump up these values if seeing horizontal scrollbars.
this.flakeRightOffset = 0; // Right margin/gutter space on edge of container
this.flakeWidth = 8; // Max pixel width reserved for snow element
this.flakeHeight = 8; // Max pixel height reserved for snow element
this.vMaxX = 5; // Maximum X velocity range for snow
this.vMaxY = 4; // Maximum Y velocity range for snow
this.zIndex = 0; // CSS stacking order applied to each snowflake
// --- "No user-serviceable parts inside" past this point, yadda yadda ---
var storm = this,
features,
// UA sniffing and backCompat rendering mode checks for fixed position, etc.
isIE = navigator.userAgent.match(/msie/i),
isIE6 = navigator.userAgent.match(/msie 6/i),
isMobile = navigator.userAgent.match(/mobile|opera m(ob|in)/i),
isBackCompatIE = (isIE && document.compatMode === 'BackCompat'),
noFixed = (isBackCompatIE || isIE6),
screenX = null, screenX2 = null, screenY = null, scrollY = null, docHeight = null, vRndX = null, vRndY = null,
windOffset = 1,
windMultiplier = 2,
flakeTypes = 6,
fixedForEverything = false,
targetElementIsRelative = false,
opacitySupported = (function(){
try {
document.createElement('div').style.opacity = '0.5';
} catch(e) {
return false;
}
return true;
}()),
didInit = false,
docFrag = document.createDocumentFragment();
features = (function() {
var getAnimationFrame;
/**
* hat tip: paul irish
* http://paulirish.com/2011/requestanimationframe-for-smart-animating/
* https://gist.github.com/838785
*/
function timeoutShim(callback) {
window.setTimeout(callback, 1000/(storm.animationInterval || 20));
}
var _animationFrame = (window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
timeoutShim);
// apply to window, avoid "illegal invocation" errors in Chrome
getAnimationFrame = _animationFrame ? function() {
return _animationFrame.apply(window, arguments);
} : null;
var testDiv;
testDiv = document.createElement('div');
function has(prop) {
// test for feature support
var result = testDiv.style[prop];
return (result !== undefined ? prop : null);
}
// note local scope.
var localFeatures = {
transform: {
ie: has('-ms-transform'),
moz: has('MozTransform'),
opera: has('OTransform'),
webkit: has('webkitTransform'),
w3: has('transform'),
prop: null // the normalized property value
},
getAnimationFrame: getAnimationFrame
};
localFeatures.transform.prop = (
localFeatures.transform.w3 ||
localFeatures.transform.moz ||
localFeatures.transform.webkit ||
localFeatures.transform.ie ||
localFeatures.transform.opera
);
testDiv = null;
return localFeatures;
}());
this.timer = null;
this.flakes = [];
this.disabled = false;
this.active = false;
this.meltFrameCount = 20;
this.meltFrames = [];
this.setXY = function(o, x, y) {
if (!o) {
return false;
}
if (storm.usePixelPosition || targetElementIsRelative) {
o.style.left = (x - storm.flakeWidth) + 'px';
o.style.top = (y - storm.flakeHeight) + 'px';
} else if (noFixed) {
o.style.right = (100-(x/screenX*100)) + '%';
// avoid creating vertical scrollbars
o.style.top = (Math.min(y, docHeight-storm.flakeHeight)) + 'px';
} else {
if (!storm.flakeBottom) {
// if not using a fixed bottom coordinate...
o.style.right = (100-(x/screenX*100)) + '%';
o.style.bottom = (100-(y/screenY*100)) + '%';
} else {
// absolute top.
o.style.right = (100-(x/screenX*100)) + '%';
o.style.top = (Math.min(y, docHeight-storm.flakeHeight)) + 'px';
}
}
};
this.events = (function() {
var old = (!window.addEventListener && window.attachEvent), slice = Array.prototype.slice,
evt = {
add: (old?'attachEvent':'addEventListener'),
remove: (old?'detachEvent':'removeEventListener')
};
function getArgs(oArgs) {
var args = slice.call(oArgs), len = args.length;
if (old) {
args[1] = 'on' + args[1]; // prefix
if (len > 3) {
args.pop(); // no capture
}
} else if (len === 3) {
args.push(false);
}
return args;
}
function apply(args, sType) {
var element = args.shift(),
method = [evt[sType]];
if (old) {
element[method](args[0], args[1]);
} else {
element[method].apply(element, args);
}
}
function addEvent() {
apply(getArgs(arguments), 'add');
}
function removeEvent() {
apply(getArgs(arguments), 'remove');
}
return {
add: addEvent,
remove: removeEvent
};
}());
function rnd(n,min) {
if (isNaN(min)) {
min = 0;
}
return (Math.random()*n)+min;
}
function plusMinus(n) {
return (parseInt(rnd(2),10)===1?n*-1:n);
}
this.randomizeWind = function() {
var i;
vRndX = plusMinus(rnd(storm.vMaxX,0.2));
vRndY = rnd(storm.vMaxY,0.2);
if (this.flakes) {
for (i=0; i<this.flakes.length; i++) {
if (this.flakes[i].active) {
this.flakes[i].setVelocities();
}
}
}
};
this.scrollHandler = function() {
var i;
// "attach" snowflakes to bottom of window if no absolute bottom value was given
scrollY = (storm.flakeBottom ? 0 : parseInt(window.scrollY || document.documentElement.scrollTop || (noFixed ? document.body.scrollTop : 0), 10));
if (isNaN(scrollY)) {
scrollY = 0; // Netscape 6 scroll fix
}
if (!fixedForEverything && !storm.flakeBottom && storm.flakes) {
for (i=0; i<storm.flakes.length; i++) {
if (storm.flakes[i].active === 0) {
storm.flakes[i].stick();
}
}
}
};
this.resizeHandler = function() {
if (window.innerWidth || window.innerHeight) {
screenX = window.innerWidth - 16 - storm.flakeRightOffset;
screenY = (storm.flakeBottom || window.innerHeight);
} else {
screenX = (document.documentElement.clientWidth || document.body.clientWidth || document.body.scrollWidth) - (!isIE ? 8 : 0) - storm.flakeRightOffset;
screenY = storm.flakeBottom || document.documentElement.clientHeight || document.body.clientHeight || document.body.scrollHeight;
}
docHeight = document.body.offsetHeight;
screenX2 = parseInt(screenX/2,10);
};
this.resizeHandlerAlt = function() {
screenX = storm.targetElement.offsetWidth - storm.flakeRightOffset;
screenY = storm.flakeBottom || storm.targetElement.offsetHeight;
screenX2 = parseInt(screenX/2,10);
docHeight = document.body.offsetHeight;
};
this.freeze = function() {
// pause animation
if (!storm.disabled) {
storm.disabled = 1;
} else {
return false;
}
storm.timer = null;
};
this.resume = function() {
if (storm.disabled) {
storm.disabled = 0;
} else {
return false;
}
storm.timerInit();
};
this.toggleSnow = function() {
if (!storm.flakes.length) {
// first run
storm.start();
} else {
storm.active = !storm.active;
if (storm.active) {
storm.show();
storm.resume();
} else {
storm.stop();
storm.freeze();
}
}
};
this.stop = function() {
var i;
this.freeze();
for (i=0; i<this.flakes.length; i++) {
this.flakes[i].o.style.display = 'none';
}
storm.events.remove(window,'scroll',storm.scrollHandler);
storm.events.remove(window,'resize',storm.resizeHandler);
if (storm.freezeOnBlur) {
if (isIE) {
storm.events.remove(document,'focusout',storm.freeze);
storm.events.remove(document,'focusin',storm.resume);
} else {
storm.events.remove(window,'blur',storm.freeze);
storm.events.remove(window,'focus',storm.resume);
}
}
};
this.show = function() {
var i;
for (i=0; i<this.flakes.length; i++) {
this.flakes[i].o.style.display = 'block';
}
};
this.SnowFlake = function(type,x,y) {
var s = this;
this.type = type;
this.x = x||parseInt(rnd(screenX-20),10);
this.y = (!isNaN(y)?y:-rnd(screenY)-12);
this.vX = null;
this.vY = null;
this.vAmpTypes = [1,1.2,1.4,1.6,1.8]; // "amplification" for vX/vY (based on flake size/type)
this.vAmp = this.vAmpTypes[this.type] || 1;
this.melting = false;
this.meltFrameCount = storm.meltFrameCount;
this.meltFrames = storm.meltFrames;
this.meltFrame = 0;
this.twinkleFrame = 0;
this.active = 1;
this.fontSize = (10+(this.type/5)*10);
this.o = document.createElement('div');
this.o.innerHTML = storm.snowCharacter;
if (storm.className) {
this.o.setAttribute('class', storm.className);
}
this.o.style.color = storm.snowColor;
this.o.style.position = (fixedForEverything?'fixed':'absolute');
if (storm.useGPU && features.transform.prop) {
// GPU-accelerated snow.
this.o.style[features.transform.prop] = 'translate3d(0px, 0px, 0px)';
}
this.o.style.width = storm.flakeWidth+'px';
this.o.style.height = storm.flakeHeight+'px';
this.o.style.fontFamily = 'arial,verdana';
this.o.style.cursor = 'default';
this.o.style.overflow = 'hidden';
this.o.style.fontWeight = 'normal';
this.o.style.zIndex = storm.zIndex;
docFrag.appendChild(this.o);
this.refresh = function() {
if (isNaN(s.x) || isNaN(s.y)) {
// safety check
return false;
}
storm.setXY(s.o, s.x, s.y);
};
this.stick = function() {
if (noFixed || (storm.targetElement !== document.documentElement && storm.targetElement !== document.body)) {
s.o.style.top = (screenY+scrollY-storm.flakeHeight)+'px';
} else if (storm.flakeBottom) {
s.o.style.top = storm.flakeBottom+'px';
} else {
s.o.style.display = 'none';
s.o.style.top = 'auto';
s.o.style.bottom = '0%';
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() {
var vX = s.vX*windOffset, yDiff;
s.x += vX;
s.y += (s.vY*s.vAmp);
if (s.x >= screenX || screenX-s.x < storm.flakeWidth) { // X-axis scroll check
s.x = 0;
} else if (vX < 0 && s.x-storm.flakeLeftOffset < -storm.flakeWidth) {
s.x = screenX-storm.flakeWidth-1; // flakeWidth;
}
s.refresh();
yDiff = screenY+scrollY-s.y+storm.flakeHeight;
if (yDiff<storm.flakeHeight) {
s.active = 0;
if (storm.snowStick) {
s.stick();
} else {
s.recycle();
}
} else {
if (storm.useMeltEffect && s.active && s.type < 3 && !s.melting && Math.random()>0.998) {
// ~1/1000 chance of melting mid-air, with each frame
s.melting = true;
s.melt();
// only incrementally melt one frame
// s.melting = false;
}
if (storm.useTwinkleEffect) {
if (s.twinkleFrame < 0) {
if (Math.random() > 0.97) {
s.twinkleFrame = parseInt(Math.random() * 8, 10);
}
} else {
s.twinkleFrame--;
if (!opacitySupported) {
s.o.style.visibility = (s.twinkleFrame && s.twinkleFrame % 2 === 0 ? 'hidden' : 'visible');
} else {
s.o.style.opacity = (s.twinkleFrame && s.twinkleFrame % 2 === 0 ? 0 : 1);
}
}
}
}
};
this.animate = function() {
// main animation loop
// move, check status, die etc.
s.move();
};
this.setVelocities = function() {
s.vX = vRndX+rnd(storm.vMaxX*0.12,0.1);
s.vY = vRndY+rnd(storm.vMaxY*0.12,0.1);
};
this.setOpacity = function(o,opacity) {
if (!opacitySupported) {
return false;
}
o.style.opacity = opacity;
};
this.melt = function() {
if (!storm.useMeltEffect || !s.melting) {
s.recycle();
} else {
if (s.meltFrame < s.meltFrameCount) {
s.setOpacity(s.o,s.meltFrames[s.meltFrame]);
s.o.style.fontSize = s.fontSize-(s.fontSize*(s.meltFrame/s.meltFrameCount))+'px';
s.o.style.lineHeight = storm.flakeHeight+2+(storm.flakeHeight*0.75*(s.meltFrame/s.meltFrameCount))+'px';
s.meltFrame++;
} else {
s.recycle();
}
}
};
this.recycle = function() {
s.o.style.display = 'none';
s.o.style.position = (fixedForEverything?'fixed':'absolute');
s.o.style.bottom = 'auto';
s.setVelocities();
s.vCheck();
s.meltFrame = 0;
s.melting = false;
s.setOpacity(s.o,1);
s.o.style.padding = '0px';
s.o.style.margin = '0px';
s.o.style.fontSize = s.fontSize+'px';
s.o.style.lineHeight = (storm.flakeHeight+2)+'px';
s.o.style.textAlign = 'center';
s.o.style.verticalAlign = 'baseline';
s.x = parseInt(rnd(screenX-storm.flakeWidth-20),10);
s.y = parseInt(rnd(screenY)*-1,10)-storm.flakeHeight;
s.refresh();
s.o.style.display = 'block';
s.active = 1;
};
this.recycle(); // set up x/y coords etc.
this.refresh();
};
this.snow = function() {
var active = 0, flake = null, i, j;
for (i=0, j=storm.flakes.length; i<j; i++) {
if (storm.flakes[i].active === 1) {
storm.flakes[i].move();
active++;
}
if (storm.flakes[i].melting) {
storm.flakes[i].melt();
}
}
if (active<storm.flakesMaxActive) {
flake = storm.flakes[parseInt(rnd(storm.flakes.length),10)];
if (flake.active === 0) {
flake.melting = true;
}
}
if (storm.timer) {
features.getAnimationFrame(storm.snow);
}
};
this.mouseMove = function(e) {
if (!storm.followMouse) {
return true;
}
var x = parseInt(e.clientX,10);
if (x<screenX2) {
windOffset = -windMultiplier+(x/screenX2*windMultiplier);
} else {
x -= screenX2;
windOffset = (x/screenX2)*windMultiplier;
}
};
this.createSnow = function(limit,allowInactive) {
var i;
for (i=0; i<limit; i++) {
storm.flakes[storm.flakes.length] = new storm.SnowFlake(parseInt(rnd(flakeTypes),10));
if (allowInactive || i>storm.flakesMaxActive) {
storm.flakes[storm.flakes.length-1].active = -1;
}
}
storm.targetElement.appendChild(docFrag);
};
this.timerInit = function() {
storm.timer = true;
storm.snow();
};
this.init = function() {
var i;
for (i=0; i<storm.meltFrameCount; i++) {
storm.meltFrames.push(1-(i/storm.meltFrameCount));
}
storm.randomizeWind();
storm.createSnow(storm.flakesMax); // create initial batch
storm.events.add(window,'resize',storm.resizeHandler);
storm.events.add(window,'scroll',storm.scrollHandler);
if (storm.freezeOnBlur) {
if (isIE) {
storm.events.add(document,'focusout',storm.freeze);
storm.events.add(document,'focusin',storm.resume);
} else {
storm.events.add(window,'blur',storm.freeze);
storm.events.add(window,'focus',storm.resume);
}
}
storm.resizeHandler();
storm.scrollHandler();
if (storm.followMouse) {
storm.events.add(isIE?document:window,'mousemove',storm.mouseMove);
}
storm.animationInterval = Math.max(20,storm.animationInterval);
storm.timerInit();
};
this.start = function(bFromOnLoad) {
if (!didInit) {
didInit = true;
} else if (bFromOnLoad) {
// already loaded and running
return true;
}
if (typeof storm.targetElement === 'string') {
var targetID = storm.targetElement;
storm.targetElement = document.getElementById(targetID);
if (!storm.targetElement) {
throw new Error('Snowstorm: Unable to get targetElement "'+targetID+'"');
}
}
if (!storm.targetElement) {
storm.targetElement = (document.body || document.documentElement);
}
if (storm.targetElement !== document.documentElement && storm.targetElement !== document.body) {
// re-map handler to get element instead of screen dimensions
storm.resizeHandler = storm.resizeHandlerAlt;
//and force-enable pixel positioning
storm.usePixelPosition = true;
}
storm.resizeHandler(); // get bounding box elements
storm.usePositionFixed = (storm.usePositionFixed && !noFixed && !storm.flakeBottom); // whether or not position:fixed is to be used
if (window.getComputedStyle) {
// attempt to determine if body or user-specified snow parent element is relatlively-positioned.
try {
targetElementIsRelative = (window.getComputedStyle(storm.targetElement, null).getPropertyValue('position') === 'relative');
} catch(e) {
// oh well
targetElementIsRelative = false;
}
}
fixedForEverything = storm.usePositionFixed;
if (screenX && screenY && !storm.disabled) {
storm.init();
storm.active = true;
}
};
function doDelayedStart() {
window.setTimeout(function() {
storm.start(true);
}, 20);
// event cleanup
storm.events.remove(isIE?document:window,'mousemove',doDelayedStart);
}
function doStart() {
if (!storm.excludeMobile || !isMobile) {
doDelayedStart();
}
// event cleanup
storm.events.remove(window, 'load', doStart);
}
// hooks for starting the snow
if (storm.autoStart) {
storm.events.add(window, 'load', doStart, false);
}
return this;
}(window, document));