Tento skript by neměl být instalován přímo. Jedná se o knihovnu, kterou by měly jiné skripty využívat pomocí meta příkazu // @require https://update.greasyfork.org/scripts/34959/229001/eisbehr%20jquery%20lazy.js
/*!
* jQuery & Zepto Lazy - v1.7.6
* http://jquery.eisbehr.de/lazy/
*
* Copyright 2012 - 2017, Daniel 'Eisbehr' Kern
*
* Dual licensed under the MIT and GPL-2.0 licenses:
* http://www.opensource.org/licenses/mit-license.php
* http://www.gnu.org/licenses/gpl-2.0.html
*
* $("img.lazy").lazy();
*/
;(function(window, undefined) {
"use strict";
// noinspection JSUnresolvedVariable
/**
* library instance - here and not in construct to be shorter in minimization
* @return void
*/
var $ = window.jQuery || window.Zepto,
/**
* unique plugin instance id counter
* @type {number}
*/
lazyInstanceId = 0,
/**
* helper to register window load for jQuery 3
* @type {boolean}
*/
windowLoaded = false;
/**
* make lazy available to jquery - and make it a bit more case-insensitive :)
* @access public
* @type {function}
* @param {object} settings
* @return void
*/
$.fn.Lazy = $.fn.lazy = function(settings) {
return new LazyPlugin(this, settings);
};
/**
* helper to add plugins to lazy prototype configuration
* @access public
* @type {function}
* @param {string|Array} names
* @param {string|Array} [elements]
* @param {function} loader
* @return void
*/
$.Lazy = $.lazy = function(names, elements, loader) {
// make second parameter optional
if( $.isFunction(elements) ) {
loader = elements;
elements = [];
}
// exit here if parameter is not a callable function
if( !$.isFunction(loader) ) {
return;
}
// make parameters an array of names to be sure
names = $.isArray(names) ? names : [names];
elements = $.isArray(elements) ? elements : [elements];
var config = LazyPlugin.prototype.config,
forced = config._f || (config._f = {});
// add the loader plugin for every name
for( var i = 0, l = names.length; i < l; i++ ) {
if( config[names[i]] === undefined || $.isFunction(config[names[i]]) ) {
config[names[i]] = loader;
}
}
// add forced elements loader
for( var c = 0, a = elements.length; c < a; c++ ) {
forced[elements[c]] = names[0];
}
};
/**
* contains all logic and the whole element handling
* is packed in a private function outside class to reduce memory usage, because it will not be created on every plugin instance
* @access private
* @type {function}
* @param {LazyPlugin} instance
* @param {object} config
* @param {object|Array} items
* @param {object} events
* @param {string} namespace
* @return void
*/
function _executeLazy(instance, config, items, events, namespace) {
/**
* a helper to trigger the 'onFinishedAll' callback after all other events
* @access private
* @type {number}
*/
var _awaitingAfterLoad = 0,
/**
* visible content width
* @access private
* @type {number}
*/
_actualWidth = -1,
/**
* visible content height
* @access private
* @type {number}
*/
_actualHeight = -1,
/**
* determine possibly detected high pixel density
* @access private
* @type {boolean}
*/
_isRetinaDisplay = false,
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_afterLoad = "afterLoad",
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_load = "load",
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_error = "error",
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_img = "img",
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_src = "src",
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_srcset = "srcset",
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_sizes = "sizes",
/**
* dictionary entry for better minimization
* @access private
* @type {string}
*/
_backgroundImage = "background-image";
/**
* initialize plugin
* bind loading to events or set delay time to load all items at once
* @access private
* @return void
*/
function _initialize() {
// detect actual device pixel ratio
// noinspection JSUnresolvedVariable
_isRetinaDisplay = window.devicePixelRatio > 1;
// prepare all initial items
items = _prepareItems(items);
// if delay time is set load all items at once after delay time
if( config.delay >= 0 ) {
setTimeout(function() {
_lazyLoadItems(true);
}, config.delay);
}
// if no delay is set or combine usage is active bind events
if( config.delay < 0 || config.combined ) {
// create unique event function
events.e = _throttle(config.throttle, function(event) {
// reset detected window size on resize event
if( event.type === "resize" ) {
_actualWidth = _actualHeight = -1;
}
// execute 'lazy magic'
_lazyLoadItems(event.all);
});
// create function to add new items to instance
events.a = function(additionalItems) {
additionalItems = _prepareItems(additionalItems);
items.push.apply(items, additionalItems);
};
// create function to get all instance items left
events.g = function() {
// filter loaded items before return in case internal filter was not running until now
return (items = $(items).filter(function() {
return !$(this).data(config.loadedName);
}));
};
// create function to force loading elements
events.f = function(forcedItems) {
for( var i = 0; i < forcedItems.length; i++ ) {
// only handle item if available in current instance
// use a compare function, because Zepto can't handle object parameter for filter
// var item = items.filter(forcedItems[i]);
/* jshint loopfunc: true */
var item = items.filter(function() {
return this === forcedItems[i];
});
if( item.length ) {
_lazyLoadItems(false, item);
}
}
};
// load initial items
_lazyLoadItems();
// bind lazy load functions to scroll and resize event
// noinspection JSUnresolvedVariable
$(config.appendScroll).on("scroll." + namespace + " resize." + namespace, events.e);
}
}
/**
* prepare items before handle them
* @access private
* @param {Array|object|jQuery} items
* @return {Array|object|jQuery}
*/
function _prepareItems(items) {
// fetch used configurations before loops
var defaultImage = config.defaultImage,
placeholder = config.placeholder,
imageBase = config.imageBase,
srcsetAttribute = config.srcsetAttribute,
loaderAttribute = config.loaderAttribute,
forcedTags = config._f || {};
// filter items and only add those who not handled yet and got needed attributes available
items = $(items).filter(function() {
var element = $(this),
tag = _getElementTagName(this);
return !element.data(config.handledName) &&
(element.attr(config.attribute) || element.attr(srcsetAttribute) || element.attr(loaderAttribute) || forcedTags[tag] !== undefined);
})
// append plugin instance to all elements
.data("plugin_" + config.name, instance);
for( var i = 0, l = items.length; i < l; i++ ) {
var element = $(items[i]),
tag = _getElementTagName(items[i]),
elementImageBase = element.attr(config.imageBaseAttribute) || imageBase;
// generate and update source set if an image base is set
if( tag === _img && elementImageBase && element.attr(srcsetAttribute) ) {
element.attr(srcsetAttribute, _getCorrectedSrcSet(element.attr(srcsetAttribute), elementImageBase));
}
// add loader to forced element types
if( forcedTags[tag] !== undefined && !element.attr(loaderAttribute) ) {
element.attr(loaderAttribute, forcedTags[tag]);
}
// set default image on every element without source
if( tag === _img && defaultImage && !element.attr(_src) ) {
element.attr(_src, defaultImage);
}
// set placeholder on every element without background image
else if( tag !== _img && placeholder && (!element.css(_backgroundImage) || element.css(_backgroundImage) === "none") ) {
element.css(_backgroundImage, "url('" + placeholder + "')");
}
}
return items;
}
/**
* the 'lazy magic' - check all items
* @access private
* @param {boolean} [allItems]
* @param {object} [forced]
* @return void
*/
function _lazyLoadItems(allItems, forced) {
// skip if no items where left
if( !items.length ) {
// destroy instance if option is enabled
if( config.autoDestroy ) {
// noinspection JSUnresolvedFunction
instance.destroy();
}
return;
}
var elements = forced || items,
loadTriggered = false,
imageBase = config.imageBase || "",
srcsetAttribute = config.srcsetAttribute,
handledName = config.handledName;
// loop all available items
for( var i = 0; i < elements.length; i++ ) {
// item is at least in loadable area
if( allItems || forced || _isInLoadableArea(elements[i]) ) {
var element = $(elements[i]),
tag = _getElementTagName(elements[i]),
attribute = element.attr(config.attribute),
elementImageBase = element.attr(config.imageBaseAttribute) || imageBase,
customLoader = element.attr(config.loaderAttribute);
// is not already handled
if( !element.data(handledName) &&
// and is visible or visibility doesn't matter
(!config.visibleOnly || element.is(":visible")) && (
// and image source or source set attribute is available
(attribute || element.attr(srcsetAttribute)) && (
// and is image tag where attribute is not equal source or source set
(tag === _img && (elementImageBase + attribute !== element.attr(_src) || element.attr(srcsetAttribute) !== element.attr(_srcset))) ||
// or is non image tag where attribute is not equal background
(tag !== _img && elementImageBase + attribute !== element.css(_backgroundImage))
) ||
// or custom loader is available
customLoader ))
{
// mark element always as handled as this point to prevent double handling
loadTriggered = true;
element.data(handledName, true);
// load item
_handleItem(element, tag, elementImageBase, customLoader);
}
}
}
// when something was loaded remove them from remaining items
if( loadTriggered ) {
items = $(items).filter(function() {
return !$(this).data(handledName);
});
}
}
/**
* load the given element the lazy way
* @access private
* @param {object} element
* @param {string} tag
* @param {string} imageBase
* @param {function} [customLoader]
* @return void
*/
function _handleItem(element, tag, imageBase, customLoader) {
// increment count of items waiting for after load
++_awaitingAfterLoad;
// extended error callback for correct 'onFinishedAll' handling
var errorCallback = function() {
_triggerCallback("onError", element);
_reduceAwaiting();
// prevent further callback calls
errorCallback = $.noop;
};
// trigger function before loading image
_triggerCallback("beforeLoad", element);
// fetch all double used data here for better code minimization
var srcAttribute = config.attribute,
srcsetAttribute = config.srcsetAttribute,
sizesAttribute = config.sizesAttribute,
retinaAttribute = config.retinaAttribute,
removeAttribute = config.removeAttribute,
loadedName = config.loadedName,
elementRetina = element.attr(retinaAttribute);
// handle custom loader
if( customLoader ) {
// on load callback
var loadCallback = function() {
// remove attribute from element
if( removeAttribute ) {
element.removeAttr(config.loaderAttribute);
}
// mark element as loaded
element.data(loadedName, true);
// call after load event
_triggerCallback(_afterLoad, element);
// remove item from waiting queue and possibly trigger finished event
// it's needed to be asynchronous to run after filter was in _lazyLoadItems
setTimeout(_reduceAwaiting, 1);
// prevent further callback calls
loadCallback = $.noop;
};
// bind error event to trigger callback and reduce waiting amount
element.off(_error).one(_error, errorCallback)
// bind after load callback to element
.one(_load, loadCallback);
// trigger custom loader and handle response
if( !_triggerCallback(customLoader, element, function(response) {
if( response ) {
element.off(_load);
loadCallback();
}
else {
element.off(_error);
errorCallback();
}
})) element.trigger(_error);
}
// handle images
else {
// create image object
var imageObj = $(new Image());
// bind error event to trigger callback and reduce waiting amount
imageObj.one(_error, errorCallback)
// bind after load callback to image
.one(_load, function() {
// remove element from view
element.hide();
// set image back to element
// do it as single 'attr' calls, to be sure 'src' is set after 'srcset'
if( tag === _img ) {
element.attr(_sizes, imageObj.attr(_sizes))
.attr(_srcset, imageObj.attr(_srcset))
.attr(_src, imageObj.attr(_src));
}
else {
element.css(_backgroundImage, "url('" + imageObj.attr(_src) + "')");
}
// bring it back with some effect!
element[config.effect](config.effectTime);
// remove attribute from element
if( removeAttribute ) {
element.removeAttr(srcAttribute + " " + srcsetAttribute + " " + retinaAttribute + " " + config.imageBaseAttribute);
// only remove 'sizes' attribute, if it was a custom one
if( sizesAttribute !== _sizes ) {
element.removeAttr(sizesAttribute);
}
}
// mark element as loaded
element.data(loadedName, true);
// call after load event
_triggerCallback(_afterLoad, element);
// cleanup image object
imageObj.remove();
// remove item from waiting queue and possibly trigger finished event
_reduceAwaiting();
});
// set sources
// do it as single 'attr' calls, to be sure 'src' is set after 'srcset'
var imageSrc = (_isRetinaDisplay && elementRetina ? elementRetina : element.attr(srcAttribute)) || "";
imageObj.attr(_sizes, element.attr(sizesAttribute))
.attr(_srcset, element.attr(srcsetAttribute))
.attr(_src, imageSrc ? imageBase + imageSrc : null);
// call after load even on cached image
imageObj.complete && imageObj.trigger(_load); // jshint ignore : line
}
}
/**
* check if the given element is inside the current viewport or threshold
* @access private
* @param {object} element
* @return {boolean}
*/
function _isInLoadableArea(element) {
var elementBound = element.getBoundingClientRect(),
direction = config.scrollDirection,
threshold = config.threshold,
vertical = // check if element is in loadable area from top
((_getActualHeight() + threshold) > elementBound.top) &&
// check if element is even in loadable are from bottom
(-threshold < elementBound.bottom),
horizontal = // check if element is in loadable area from left
((_getActualWidth() + threshold) > elementBound.left) &&
// check if element is even in loadable area from right
(-threshold < elementBound.right);
if( direction === "vertical" ) {
return vertical;
}
else if( direction === "horizontal" ) {
return horizontal;
}
return vertical && horizontal;
}
/**
* receive the current viewed width of the browser
* @access private
* @return {number}
*/
function _getActualWidth() {
return _actualWidth >= 0 ? _actualWidth : (_actualWidth = $(window).width());
}
/**
* receive the current viewed height of the browser
* @access private
* @return {number}
*/
function _getActualHeight() {
return _actualHeight >= 0 ? _actualHeight : (_actualHeight = $(window).height());
}
/**
* get lowercase tag name of an element
* @access private
* @param {object} element
* @returns {string}
*/
function _getElementTagName(element) {
return element.tagName.toLowerCase();
}
/**
* prepend image base to all srcset entries
* @access private
* @param {string} srcset
* @param {string} imageBase
* @returns {string}
*/
function _getCorrectedSrcSet(srcset, imageBase) {
if( imageBase ) {
// trim, remove unnecessary spaces and split entries
var entries = srcset.split(",");
srcset = "";
for( var i = 0, l = entries.length; i < l; i++ ) {
srcset += imageBase + entries[i].trim() + (i !== l - 1 ? "," : "");
}
}
return srcset;
}
/**
* helper function to throttle down event triggering
* @access private
* @param {number} delay
* @param {function} callback
* @return {function}
*/
function _throttle(delay, callback) {
var timeout,
lastExecute = 0;
return function(event, ignoreThrottle) {
var elapsed = +new Date() - lastExecute;
function run() {
lastExecute = +new Date();
// noinspection JSUnresolvedFunction
callback.call(instance, event);
}
timeout && clearTimeout(timeout); // jshint ignore : line
if( elapsed > delay || !config.enableThrottle || ignoreThrottle ) {
run();
}
else {
timeout = setTimeout(run, delay - elapsed);
}
};
}
/**
* reduce count of awaiting elements to 'afterLoad' event and fire 'onFinishedAll' if reached zero
* @access private
* @return void
*/
function _reduceAwaiting() {
--_awaitingAfterLoad;
// if no items were left trigger finished event
if( !items.length && !_awaitingAfterLoad ) {
_triggerCallback("onFinishedAll");
}
}
/**
* single implementation to handle callbacks, pass element and set 'this' to current instance
* @access private
* @param {string|function} callback
* @param {object} [element]
* @param {*} [args]
* @return {boolean}
*/
function _triggerCallback(callback, element, args) {
if( (callback = config[callback]) ) {
// jQuery's internal '$(arguments).slice(1)' are causing problems at least on old iPads
// below is shorthand of 'Array.prototype.slice.call(arguments, 1)'
callback.apply(instance, [].slice.call(arguments, 1));
return true;
}
return false;
}
// if event driven or window is already loaded don't wait for page loading
if( config.bind === "event" || windowLoaded ) {
_initialize();
}
// otherwise load initial items and start lazy after page load
else {
// noinspection JSUnresolvedVariable
$(window).on(_load + "." + namespace, _initialize);
}
}
/**
* lazy plugin class constructor
* @constructor
* @access private
* @param {object} elements
* @param {object} settings
* @return {object|LazyPlugin}
*/
function LazyPlugin(elements, settings) {
/**
* this lazy plugin instance
* @access private
* @type {object|LazyPlugin|LazyPlugin.prototype}
*/
var _instance = this,
/**
* this lazy plugin instance configuration
* @access private
* @type {object}
*/
_config = $.extend({}, _instance.config, settings),
/**
* instance generated event executed on container scroll or resize
* packed in an object to be referenceable and short named because properties will not be minified
* @access private
* @type {object}
*/
_events = {},
/**
* unique namespace for instance related events
* @access private
* @type {string}
*/
_namespace = _config.name + "-" + (++lazyInstanceId);
// noinspection JSUndefinedPropertyAssignment
/**
* wrapper to get or set an entry from plugin instance configuration
* much smaller on minify as direct access
* @access public
* @type {function}
* @param {string} entryName
* @param {*} [value]
* @return {LazyPlugin|*}
*/
_instance.config = function(entryName, value) {
if( value === undefined ) {
return _config[entryName];
}
_config[entryName] = value;
return _instance;
};
// noinspection JSUndefinedPropertyAssignment
/**
* add additional items to current instance
* @access public
* @param {Array|object|string} items
* @return {LazyPlugin}
*/
_instance.addItems = function(items) {
_events.a && _events.a($.type(items) === "string" ? $(items) : items); // jshint ignore : line
return _instance;
};
// noinspection JSUndefinedPropertyAssignment
/**
* get all left items of this instance
* @access public
* @returns {object}
*/
_instance.getItems = function() {
return _events.g ? _events.g() : {};
};
// noinspection JSUndefinedPropertyAssignment
/**
* force lazy to load all items in loadable area right now
* by default without throttle
* @access public
* @type {function}
* @param {boolean} [useThrottle]
* @return {LazyPlugin}
*/
_instance.update = function(useThrottle) {
_events.e && _events.e({}, !useThrottle); // jshint ignore : line
return _instance;
};
// noinspection JSUndefinedPropertyAssignment
/**
* force element(s) to load directly, ignoring the viewport
* @access public
* @param {Array|object|string} items
* @return {LazyPlugin}
*/
_instance.force = function(items) {
_events.f && _events.f($.type(items) === "string" ? $(items) : items); // jshint ignore : line
return _instance;
};
// noinspection JSUndefinedPropertyAssignment
/**
* force lazy to load all available items right now
* this call ignores throttling
* @access public
* @type {function}
* @return {LazyPlugin}
*/
_instance.loadAll = function() {
_events.e && _events.e({all: true}, true); // jshint ignore : line
return _instance;
};
// noinspection JSUndefinedPropertyAssignment
/**
* destroy this plugin instance
* @access public
* @type {function}
* @return undefined
*/
_instance.destroy = function() {
// unbind instance generated events
// noinspection JSUnresolvedFunction, JSUnresolvedVariable
$(_config.appendScroll).off("." + _namespace, _events.e);
// noinspection JSUnresolvedVariable
$(window).off("." + _namespace);
// clear events
_events = {};
return undefined;
};
// start using lazy and return all elements to be chainable or instance for further use
// noinspection JSUnresolvedVariable
_executeLazy(_instance, _config, elements, _events, _namespace);
return _config.chainable ? elements : _instance;
}
/**
* settings and configuration data
* @access public
* @type {object}
*/
LazyPlugin.prototype.config = {
// general
name : "lazy",
chainable : true,
autoDestroy : true,
bind : "load",
threshold : 500,
visibleOnly : false,
appendScroll : window,
scrollDirection : "both",
imageBase : null,
defaultImage : "data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==",
placeholder : null,
delay : -1,
combined : false,
// attributes
attribute : "data-src",
srcsetAttribute : "data-srcset",
sizesAttribute : "data-sizes",
retinaAttribute : "data-retina",
loaderAttribute : "data-loader",
imageBaseAttribute : "data-imagebase",
removeAttribute : true,
handledName : "handled",
loadedName : "loaded",
// effect
effect : "show",
effectTime : 0,
// throttle
enableThrottle : true,
throttle : 250,
// callbacks
beforeLoad : undefined,
afterLoad : undefined,
onError : undefined,
onFinishedAll : undefined
};
// register window load event globally to prevent not loading elements
// since jQuery 3.X ready state is fully async and may be executed after 'load'
$(window).on("load", function() {
windowLoaded = true;
});
})(window);
