Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
// SmoothScroll for websites v1.2.1
// Licensed under the terms of the MIT license.
// People involved
// - Balazs Galambosi (maintainer)
// - Michael Herf (Pulse Algorithm)
(function(){
// Scroll Variables (tweakable)
var defaultOptions = {
// Scrolling Core
frameRate : 150, // [Hz]
animationTime : 400, // [px]
stepSize : 120, // [px]
// Pulse (less tweakable)
// ratio of "tail" to "acceleration"
pulseAlgorithm : true,
pulseScale : 8,
pulseNormalize : 1,
// Acceleration
accelerationDelta : 20, // 20
accelerationMax : 1, // 1
// Keyboard Settings
keyboardSupport : true, // option
arrowScroll : 50, // [px]
// Other
touchpadSupport : true,
fixedBackground : true,
excluded : ""
};
var options = defaultOptions;
// Other Variables
var isExcluded = false;
var isFrame = false;
var direction = { x: 0, y: 0 };
var initDone = false;
var root = document.documentElement;
var activeElement;
var observer;
var deltaBuffer = [ 120, 120, 120 ];
var key = { left: 37, up: 38, right: 39, down: 40, spacebar: 32,
pageup: 33, pagedown: 34, end: 35, home: 36 };
/***********************************************
* SETTINGS
***********************************************/
var options = defaultOptions;
/***********************************************
* INITIALIZE
***********************************************/
/**
* Tests if smooth scrolling is allowed. Shuts down everything if not.
*/
function initTest() {
var disableKeyboard = false;
// disable keyboard support if anything above requested it
if (disableKeyboard) {
removeEvent("keydown", keydown);
}
if (options.keyboardSupport && !disableKeyboard) {
addEvent("keydown", keydown);
}
}
/**
* Sets up scrolls array, determines if frames are involved.
*/
function init() {
if (!document.body) return;
var body = document.body;
var html = document.documentElement;
var windowHeight = window.innerHeight;
var scrollHeight = body.scrollHeight;
// check compat mode for root element
root = (document.compatMode.indexOf('CSS') >= 0) ? html : body;
activeElement = body;
initTest();
initDone = true;
// Checks if this script is running in a frame
if (top != self) {
isFrame = true;
}
/**
* This fixes a bug where the areas left and right to
* the content does not trigger the onmousewheel event
* on some pages. e.g.: html, body { height: 100% }
*/
else if (scrollHeight > windowHeight &&
(body.offsetHeight <= windowHeight ||
html.offsetHeight <= windowHeight)) {
// DOMChange (throttle): fix height
var pending = false;
var refresh = function () {
if (!pending && html.scrollHeight != document.height) {
pending = true; // add a new pending action
setTimeout(function () {
html.style.height = document.height + 'px';
pending = false;
}, 500); // act rarely to stay fast
}
};
html.style.height = 'auto';
setTimeout(refresh, 10);
// clearfix
if (root.offsetHeight <= windowHeight) {
var underlay = document.createElement("div");
underlay.style.clear = "both";
body.appendChild(underlay);
}
}
// disable fixed background
if (!options.fixedBackground && !isExcluded) {
body.style.backgroundAttachment = "scroll";
html.style.backgroundAttachment = "scroll";
}
}
/************************************************
* SCROLLING
************************************************/
var que = [];
var pending = false;
var lastScroll = +new Date;
/**
* Pushes scroll actions to the scrolling queue.
*/
function scrollArray(elem, left, top, delay) {
delay || (delay = 1000);
directionCheck(left, top);
if (options.accelerationMax != 1) {
var now = +new Date;
var elapsed = now - lastScroll;
if (elapsed < options.accelerationDelta) {
var factor = (1 + (30 / elapsed)) / 2;
if (factor > 1) {
factor = Math.min(factor, options.accelerationMax);
left *= factor;
top *= factor;
}
}
lastScroll = +new Date;
}
// push a scroll command
que.push({
x: left,
y: top,
lastX: (left < 0) ? 0.99 : -0.99,
lastY: (top < 0) ? 0.99 : -0.99,
start: +new Date
});
// don't act if there's a pending queue
if (pending) {
return;
}
var scrollWindow = (elem === document.body);
var step = function (time) {
var now = +new Date;
var scrollX = 0;
var scrollY = 0;
for (var i = 0; i < que.length; i++) {
var item = que[i];
var elapsed = now - item.start;
var finished = (elapsed >= options.animationTime);
// scroll position: [0, 1]
var position = (finished) ? 1 : elapsed / options.animationTime;
// easing [optional]
if (options.pulseAlgorithm) {
position = pulse(position);
}
// only need the difference
var x = (item.x * position - item.lastX) >> 0;
var y = (item.y * position - item.lastY) >> 0;
// add this to the total scrolling
scrollX += x;
scrollY += y;
// update last values
item.lastX += x;
item.lastY += y;
// delete and step back if it's over
if (finished) {
que.splice(i, 1); i--;
}
}
// scroll left and top
if (scrollWindow) {
window.scrollBy(scrollX, scrollY);
}
else {
if (scrollX) elem.scrollLeft += scrollX;
if (scrollY) elem.scrollTop += scrollY;
}
// clean up if there's nothing left to do
if (!left && !top) {
que = [];
}
if (que.length) {
requestFrame(step, elem, (delay / options.frameRate + 1));
} else {
pending = false;
}
};
// start a new queue of actions
requestFrame(step, elem, 0);
pending = true;
}
/***********************************************
* EVENTS
***********************************************/
/**
* Mouse wheel handler.
* @param {Object} event
*/
function wheel(event) {
if (!initDone) {
init();
}
var target = event.target;
var overflowing = overflowingAncestor(target);
// use default if there's no overflowing
// element or default action is prevented
if (!overflowing || event.defaultPrevented ||
isNodeName(activeElement, "embed") ||
(isNodeName(target, "embed") && /\.pdf/i.test(target.src))) {
return true;
}
var deltaX = event.wheelDeltaX || 0;
var deltaY = event.wheelDeltaY || 0;
// use wheelDelta if deltaX/Y is not available
if (!deltaX && !deltaY) {
deltaY = event.wheelDelta || 0;
}
// check if it's a touchpad scroll that should be ignored
if (!options.touchpadSupport && isTouchpad(deltaY)) {
return true;
}
// scale by step size
// delta is 120 most of the time
// synaptics seems to send 1 sometimes
if (Math.abs(deltaX) > 1.2) {
deltaX *= options.stepSize / 120;
}
if (Math.abs(deltaY) > 1.2) {
deltaY *= options.stepSize / 120;
}
scrollArray(overflowing, -deltaX, -deltaY);
event.preventDefault();
}
/**
* Keydown event handler.
* @param {Object} event
*/
function keydown(event) {
var target = event.target;
var modifier = event.ctrlKey || event.altKey || event.metaKey ||
(event.shiftKey && event.keyCode !== key.spacebar);
// do nothing if user is editing text
// or using a modifier key (except shift)
// or in a dropdown
if ( /input|textarea|select|embed/i.test(target.nodeName) ||
target.isContentEditable ||
event.defaultPrevented ||
modifier ) {
return true;
}
// spacebar should trigger button press
if (isNodeName(target, "button") &&
event.keyCode === key.spacebar) {
return true;
}
var shift, x = 0, y = 0;
var elem = overflowingAncestor(activeElement);
var clientHeight = elem.clientHeight;
if (elem == document.body) {
clientHeight = window.innerHeight;
}
switch (event.keyCode) {
case key.up:
y = -options.arrowScroll;
break;
case key.down:
y = options.arrowScroll;
break;
case key.spacebar: // (+ shift)
shift = event.shiftKey ? 1 : -1;
y = -shift * clientHeight * 0.9;
break;
case key.pageup:
y = -clientHeight * 0.9;
break;
case key.pagedown:
y = clientHeight * 0.9;
break;
case key.home:
y = -elem.scrollTop;
break;
case key.end:
var damt = elem.scrollHeight - elem.scrollTop - clientHeight;
y = (damt > 0) ? damt+10 : 0;
break;
case key.left:
x = -options.arrowScroll;
break;
case key.right:
x = options.arrowScroll;
break;
default:
return true; // a key we don't care about
}
scrollArray(elem, x, y);
event.preventDefault();
}
/**
* Mousedown event only for updating activeElement
*/
function mousedown(event) {
activeElement = event.target;
}
/***********************************************
* OVERFLOW
***********************************************/
var cache = {}; // cleared out every once in while
setInterval(function () { cache = {}; }, 10 * 1000);
var uniqueID = (function () {
var i = 0;
return function (el) {
return el.uniqueID || (el.uniqueID = i++);
};
})();
function setCache(elems, overflowing) {
for (var i = elems.length; i--;)
cache[uniqueID(elems[i])] = overflowing;
return overflowing;
}
function overflowingAncestor(el) {
var elems = [];
var rootScrollHeight = root.scrollHeight;
do {
var cached = cache[uniqueID(el)];
if (cached) {
return setCache(elems, cached);
}
elems.push(el);
if (rootScrollHeight === el.scrollHeight) {
if (!isFrame || root.clientHeight + 10 < rootScrollHeight) {
return setCache(elems, document.body); // scrolling root in WebKit
}
} else if (el.clientHeight + 10 < el.scrollHeight) {
overflow = getComputedStyle(el, "").getPropertyValue("overflow-y");
if (overflow === "scroll" || overflow === "auto") {
return setCache(elems, el);
}
}
} while (el = el.parentNode);
}
/***********************************************
* HELPERS
***********************************************/
function addEvent(type, fn, bubble) {
window.addEventListener(type, fn, (bubble||false));
}
function removeEvent(type, fn, bubble) {
window.removeEventListener(type, fn, (bubble||false));
}
function isNodeName(el, tag) {
return (el.nodeName||"").toLowerCase() === tag.toLowerCase();
}
function directionCheck(x, y) {
x = (x > 0) ? 1 : -1;
y = (y > 0) ? 1 : -1;
if (direction.x !== x || direction.y !== y) {
direction.x = x;
direction.y = y;
que = [];
lastScroll = 0;
}
}
var deltaBufferTimer;
function isTouchpad(deltaY) {
if (!deltaY) return;
deltaY = Math.abs(deltaY)
deltaBuffer.push(deltaY);
deltaBuffer.shift();
clearTimeout(deltaBufferTimer);
var allDivisable = (isDivisible(deltaBuffer[0], 120) &&
isDivisible(deltaBuffer[1], 120) &&
isDivisible(deltaBuffer[2], 120));
return !allDivisable;
}
function isDivisible(n, divisor) {
return (Math.floor(n / divisor) == n / divisor);
}
var requestFrame = (function () {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
function (callback, element, delay) {
window.setTimeout(callback, delay || (1000/60));
};
})();
/***********************************************
* PULSE
***********************************************/
/**
* Viscous fluid with a pulse for part and decay for the rest.
* - Applies a fixed force over an interval (a damped acceleration), and
* - Lets the exponential bleed away the velocity over a longer interval
* - Michael Herf, http://stereopsis.com/stopping/
*/
function pulse_(x) {
var val, start, expx;
// test
x = x * options.pulseScale;
if (x < 1) { // acceleartion
val = x - (1 - Math.exp(-x));
} else { // tail
// the previous animation ended here:
start = Math.exp(-1);
// simple viscous drag
x -= 1;
expx = 1 - Math.exp(-x);
val = start + (expx * (1 - start));
}
return val * options.pulseNormalize;
}
function pulse(x) {
if (x >= 1) return 1;
if (x <= 0) return 0;
if (options.pulseNormalize == 1) {
options.pulseNormalize /= pulse_(1);
}
return pulse_(x);
}
var isChrome = /chrome/i.test(window.navigator.userAgent);
var wheelEvent = null;
if ("onwheel" in document.createElement("div"))
wheelEvent = "wheel";
else if ("onmousewheel" in document.createElement("div"))
wheelEvent = "mousewheel";
if (wheelEvent && isChrome) {
addEvent(wheelEvent, wheel);
addEvent("mousedown", mousedown);
addEvent("load", init);
}
})();
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.