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jquery.lazyloadxt.js
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jquery.lazyloadxt.js
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/*! Lazy Load XT v0.8.10 2014-01-07
* http://ressio.github.io/lazy-load-xt
* (C) 2014 RESS.io
* Licensed under MIT */
(function ($, window, document, undefined) {
// options
var options = {
autoInit: true,
selector: 'img',
classNojs: 'lazy',
blankImage: 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7',
throttle: 99,
loadEvent: 'pageshow', // check AJAX-loaded content in jQueryMobile
updateEvent: 'load orientationchange resize scroll', // page-modified events
forceEvent: '', // force loading of all elements
oninit: null, // init handler
onshow: null, // start loading handler
onload: null, // load success handler
onerror: null // error handler
},
elementOptions = {
srcAttr: 'data-src',
edgeX: 0,
edgeY: 0,
visibleOnly: true
},
$window = $(window),
dataLazied = 'lazied',
elements = [],
viewportTop,
viewportBottom,
viewportLeft,
viewportRight,
$data = $.data || function (el, name) {
return $(el).data(name);
},
topLazy = 0,
/*
waitingMode=0 : no setTimeout
waitingMode=1 : setTimeout, no deferred events
waitingMode=2 : setTimeout, deferred events
*/
waitingMode = 0;
$.lazyLoadXT = $.extend(options, elementOptions, $.lazyLoadXT);
/**
* Add new elements to lazy-load list:
* $(elements).lazyLoadXT() or $(window).lazyLoadXT()
*
* @param {object} [overrides] loading of all elements
*/
$.fn.lazyLoadXT = function (overrides) {
overrides = overrides || {};
var elementOptionsOverrides = {},
blankImage = overrides.blankImage || options.blankImage,
classNojs = overrides.classNojs || options.classNojs,
checkDuplicates = overrides.checkDuplicates || true,
prop;
for (prop in elementOptions) {
elementOptionsOverrides[prop] = (overrides[prop] === undefined) ? options[prop] : overrides[prop];
}
return this.each(function () {
if (this === window) {
$(options.selector).lazyLoadXT(overrides);
} else {
// prevent duplicates
if (checkDuplicates && $data(this, dataLazied)) {
return;
}
var $el = $(this);
$el
.data(dataLazied, 1)
.removeClass(classNojs);
if (blankImage && $el[0].tagName === 'IMG' && !$el.attr('src')) {
$el.attr('src', blankImage);
}
// clone elementOptionsOverrides object
$el.lazyLoadXT = $.extend({}, elementOptionsOverrides);
triggerEvent('init', $el);
elements.unshift($el); // push it in the first position as we iterate elements in reverse order
}
});
};
/**
* Save visible viewport boundary to viewportXXX variables
*/
function calcViewport() {
viewportTop = $window.scrollTop();
viewportBottom = viewportTop + (window.innerHeight || $window.height());
viewportLeft = window.pageXOffset || 0;
viewportRight = viewportLeft + (window.innerWidth || $window.width());
}
/**
* Process function/object event handler
* @param {string} event suffix
* @param {jQuery} $el
*/
function triggerEvent(event, $el) {
$el.trigger('lazy' + event, [$el]);
var handler = options['on' + event];
if (handler) {
if ($.isFunction(handler)) {
handler.call($el[0]);
} else {
$el
.addClass(handler.addClass)
.removeClass(handler.removeClass);
}
}
// queue next check as images may be resized after loading of actual file
queueCheckLazyElements();
}
/**
* Trigger onload/onerror handler
* @param {Event} e
*/
function triggerLoadOrError(e) {
triggerEvent(e.type, $(this).off('load error', triggerLoadOrError));
}
/**
* Load visible elements
* @param {bool} [force] loading of all elements
*/
function checkLazyElements(force) {
if (!elements.length) {
return;
}
topLazy = Infinity;
calcViewport();
for (var i = elements.length - 1; i >= 0; i--) {
var $el = elements[i],
el = $el[0],
objData = $el.lazyLoadXT;
// remove items that are not in DOM
if (!$.contains(document.documentElement, el)) {
elements.splice(i, 1);
} else if (force || !objData.visibleOnly || el.offsetWidth > 0 || el.offsetHeight > 0) {
var offset = $el.offset(),
elTop = offset.top,
elLeft = offset.left,
edgeX = objData.edgeX,
edgeY = objData.edgeY,
topEdge = elTop - edgeY;
if (force ||
((topEdge <= viewportBottom) && (elTop + $el.height() > viewportTop - edgeY) &&
(elLeft <= viewportRight + edgeX) && (elLeft + $el.width() > viewportLeft - edgeX))) {
triggerEvent('show', $el);
var srcAttr = objData.srcAttr,
src = $.isFunction(srcAttr) ? srcAttr($el) : $el.attr(srcAttr);
if (src) {
$el
.on('load error', triggerLoadOrError)
.attr('src', src);
}
elements.splice(i, 1);
} else {
if (topEdge < topLazy) {
topLazy = topEdge;
}
}
}
}
if (!elements.length) {
$(document).trigger('lazyloadall');
}
}
/**
* Run check of lazy elements after timeout
*/
function timeoutLazyElements() {
if (waitingMode > 1) {
waitingMode = 1;
checkLazyElements();
setTimeout(timeoutLazyElements, options.throttle);
} else {
waitingMode = 0;
}
}
/**
* Queue check of lazy elements because of event e
* @param {Event} [e]
*/
function queueCheckLazyElements(e) {
if (!elements.length) {
return;
}
// fast check for scroll event without new visible elements
if (e && e.type === 'scroll') {
calcViewport();
if (topLazy >= viewportBottom) {
return;
}
}
if (!waitingMode) {
setTimeout(timeoutLazyElements, 0);
}
waitingMode = 2;
}
/**
* Initialize list of hidden elements
*/
function initLazyElements() {
$window.lazyLoadXT();
queueCheckLazyElements();
}
/**
* Loading of all elements
*/
function forceLoadAll() {
checkLazyElements(true);
}
/**
* Initialization
*/
$(document).ready(function () {
$window
.on(options.loadEvent, initLazyElements)
.on(options.updateEvent, queueCheckLazyElements)
.on(options.forceEvent, forceLoadAll);
if (options.autoInit) {
initLazyElements(); // standard initialization
}
});
})(window.jQuery || window.Zepto, window, document);