inobounce.js
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/*! iNoBounce - v0.2.0
* https://github.com/lazd/iNoBounce/
* Copyright (c) 2013 Larry Davis <lazdnet@gmail.com>; Licensed BSD */
(function(global) {
// Stores the Y position where the touch started
var startY = 0;
// Store enabled status
var enabled = false;
var supportsPassiveOption = false;
try {
var opts = Object.defineProperty({}, 'passive', {
get: function() {
supportsPassiveOption = true;
}
});
window.addEventListener('test', null, opts);
} catch (e) {}
var handleTouchmove = function(evt) {
// Get the element that was scrolled upon
var el = evt.target;
// Allow zooming
var zoom = window.innerWidth / window.document.documentElement.clientWidth;
if (evt.touches.length > 1 || zoom !== 1) {
return;
}
// Check all parent elements for scrollability
while (el !== document.body && el !== document) {
// Get some style properties
var style = window.getComputedStyle(el);
if (!style) {
// If we've encountered an element we can't compute the style for, get out
break;
}
// Ignore range input element
if (el.nodeName === 'INPUT' && el.getAttribute('type') === 'range') {
return;
}
var scrolling = style.getPropertyValue('-webkit-overflow-scrolling');
var overflowY = style.getPropertyValue('overflow-y');
var height = parseInt(style.getPropertyValue('height'), 10);
// Determine if the element should scroll
var isScrollable = scrolling === 'touch' && (overflowY === 'auto' || overflowY === 'scroll');
var canScroll = el.scrollHeight > el.offsetHeight;
if (isScrollable && canScroll) {
// Get the current Y position of the touch
var curY = evt.touches ? evt.touches[0].screenY : evt.screenY;
// Determine if the user is trying to scroll past the top or bottom
// In this case, the window will bounce, so we have to prevent scrolling completely
var isAtTop = (startY <= curY && el.scrollTop === 0);
var isAtBottom = (startY >= curY && el.scrollHeight - el.scrollTop === height);
// Stop a bounce bug when at the bottom or top of the scrollable element
if (isAtTop || isAtBottom) {
evt.preventDefault();
}
// No need to continue up the DOM, we've done our job
return;
}
// Test the next parent
el = el.parentNode;
}
// Stop the bouncing -- no parents are scrollable
evt.preventDefault();
};
var handleTouchstart = function(evt) {
// Store the first Y position of the touch
startY = evt.touches ? evt.touches[0].screenY : evt.screenY;
};
var enable = function() {
// Listen to a couple key touch events
window.addEventListener('touchstart', handleTouchstart, supportsPassiveOption ? { passive : false } : false);
window.addEventListener('touchmove', handleTouchmove, supportsPassiveOption ? { passive : false } : false);
enabled = true;
};
var disable = function() {
// Stop listening
window.removeEventListener('touchstart', handleTouchstart, false);
window.removeEventListener('touchmove', handleTouchmove, false);
enabled = false;
};
var isEnabled = function() {
return enabled;
};
// Enable by default if the browser supports -webkit-overflow-scrolling
// Test this by setting the property with JavaScript on an element that exists in the DOM
// Then, see if the property is reflected in the computed style
var testDiv = document.createElement('div');
document.documentElement.appendChild(testDiv);
testDiv.style.WebkitOverflowScrolling = 'touch';
var isScrollSupported = 'getComputedStyle' in window && window.getComputedStyle(testDiv)['-webkit-overflow-scrolling'] === 'touch';
document.documentElement.removeChild(testDiv);
if (isScrollSupported) {
enable();
}
// A module to support enabling/disabling iNoBounce
var iNoBounce = {
enable: enable,
disable: disable,
isEnabled: isEnabled,
isScrollSupported: isScrollSupported
};
if (typeof module !== 'undefined' && module.exports) {
// Node.js Support
module.exports = iNoBounce;
}
if (typeof global.define === 'function') {
// AMD Support
(function(define) {
define('iNoBounce', [], function() { return iNoBounce; });
}(global.define));
}
else {
// Browser support
global.iNoBounce = iNoBounce;
}
}(this));