135 lines
3.7 KiB
JavaScript
135 lines
3.7 KiB
JavaScript
(function (global, factory) {
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if (typeof exports === "object" && typeof module !== "undefined") {
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module.exports = factory(global.document);
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}
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else if (typeof define === "function" && define.amd) {
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define([global.document], factory);
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} else {
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global = global || self;
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global.echo = factory(global.document);
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}
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})(this, function (root) {
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"use strict";
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var echo = {};
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var callback = function () {};
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var offset, poll, delay, useDebounce, unload;
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var isHidden = function (element) {
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return (element.offsetParent === null);
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};
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var inView = function (element, view) {
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if (isHidden(element)) {
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return false;
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}
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var box = element.getBoundingClientRect();
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return (box.right >= view.l && box.bottom >= view.t && box.left <= view.r && box.top <= view.b);
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};
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var debounceOrThrottle = function () {
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if(!useDebounce && !!poll) {
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return;
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}
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clearTimeout(poll);
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poll = setTimeout(function(){
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echo.render();
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poll = null;
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}, delay);
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};
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echo.init = function (opts) {
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opts = opts || {};
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var offsetAll = opts.offset || 0;
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var offsetVertical = opts.offsetVertical || offsetAll;
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var offsetHorizontal = opts.offsetHorizontal || offsetAll;
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var optionToInt = function (opt, fallback) {
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return parseInt(opt || fallback, 10);
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};
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offset = {
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t: optionToInt(opts.offsetTop, offsetVertical),
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b: optionToInt(opts.offsetBottom, offsetVertical),
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l: optionToInt(opts.offsetLeft, offsetHorizontal),
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r: optionToInt(opts.offsetRight, offsetHorizontal)
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};
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delay = optionToInt(opts.throttle, 250);
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useDebounce = opts.debounce !== false;
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unload = !!opts.unload;
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callback = opts.callback || callback;
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echo.render();
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if (document.addEventListener) {
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root.addEventListener("scroll", debounceOrThrottle, false);
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root.addEventListener("load", debounceOrThrottle, false);
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} else {
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root.attachEvent("onscroll", debounceOrThrottle);
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root.attachEvent("onload", debounceOrThrottle);
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}
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};
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echo.render = function () {
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var nodes = document.querySelectorAll("img[data-echo], [data-echo-background]");
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var length = nodes.length;
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var src, elem;
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var view = {
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l: 0 - offset.l,
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t: 0 - offset.t,
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b: (root.innerHeight || document.documentElement.clientHeight) + offset.b,
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r: (root.innerWidth || document.documentElement.clientWidth) + offset.r
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};
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for (var i = 0; i < length; i++) {
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elem = nodes[i];
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if (inView(elem, view)) {
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if (unload) {
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elem.setAttribute("data-echo-placeholder", elem.src);
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}
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if (elem.getAttribute("data-echo-background") !== null) {
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elem.style.backgroundImage = "url(" + elem.getAttribute("data-echo-background") + ")";
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}
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else {
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elem.src = elem.getAttribute("data-echo");
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}
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if (!unload) {
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elem.removeAttribute("data-echo");
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elem.removeAttribute("data-echo-background");
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}
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callback(elem, "load");
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}
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else if (unload && !!(src = elem.getAttribute("data-echo-placeholder"))) {
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if (elem.getAttribute("data-echo-background") !== null) {
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elem.style.backgroundImage = "url(" + src + ")";
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}
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else {
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elem.src = src;
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}
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elem.removeAttribute("data-echo-placeholder");
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callback(elem, "unload");
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}
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}
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if (!length) {
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echo.detach();
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}
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};
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echo.detach = function () {
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if (document.removeEventListener) {
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root.removeEventListener("scroll", debounceOrThrottle);
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} else {
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root.detachEvent("onscroll", debounceOrThrottle);
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}
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clearTimeout(poll);
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};
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return echo;
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});
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