feat: Avoid setting elem.src if unchanged (#113)

* Avoid setting elem.src if unchanged

Helps with non-img elements on Firefox.
Prevents reloading on scroll.

* lint: single-quoted strings

* dist: update with latest source

dist/echo.js

@@ -71,8 +71,8 @@
     }
   };
 
-  echo.render = function () {
+  echo.render = function (context) {
-    var nodes = document.querySelectorAll('img[data-echo], [data-echo-background]');
+    var nodes = (context || document).querySelectorAll('[data-echo], [data-echo-background]');
     var length = nodes.length;
     var src, elem;
     var view = {
@@ -90,10 +90,10 @@
         }
 
         if (elem.getAttribute('data-echo-background') !== null) {
-          elem.style.backgroundImage = "url(" + elem.getAttribute('data-echo-background') + ")";
+          elem.style.backgroundImage = 'url(' + elem.getAttribute('data-echo-background') + ')';
         }
-        else {
+        else if (elem.src !== (src = elem.getAttribute('data-echo'))) {
-          elem.src = elem.getAttribute('data-echo');
+          elem.src = src;
         }
 
         if (!unload) {
@@ -106,7 +106,7 @@
       else if (unload && !!(src = elem.getAttribute('data-echo-placeholder'))) {
 
         if (elem.getAttribute('data-echo-background') !== null) {
-          elem.style.backgroundImage = "url(" + src + ")";
+          elem.style.backgroundImage = 'url(' + src + ')';
         }
         else {
           elem.src = src;

dist/echo.min.js

@@ -1,2 +1,2 @@
 /*! echo-js v1.7.3 | (c) 2016 @toddmotto | https://github.com/toddmotto/echo */
-!function(t,e){"function"==typeof define&&define.amd?define(function(){return e(t)}):"object"==typeof exports?module.exports=e:t.echo=e(t)}(this,function(t){"use strict";var e,n,o,r,c,a={},u=function(){},d=function(t){return null===t.offsetParent},i=function(t,e){if(d(t))return!1;var n=t.getBoundingClientRect();return n.right>=e.l&&n.bottom>=e.t&&n.left<=e.r&&n.top<=e.b},l=function(){(r||!n)&&(clearTimeout(n),n=setTimeout(function(){a.render(),n=null},o))};return a.init=function(n){n=n||{};var d=n.offset||0,i=n.offsetVertical||d,f=n.offsetHorizontal||d,s=function(t,e){return parseInt(t||e,10)};e={t:s(n.offsetTop,i),b:s(n.offsetBottom,i),l:s(n.offsetLeft,f),r:s(n.offsetRight,f)},o=s(n.throttle,250),r=n.debounce!==!1,c=!!n.unload,u=n.callback||u,a.render(),document.addEventListener?(t.addEventListener("scroll",l,!1),t.addEventListener("load",l,!1)):(t.attachEvent("onscroll",l),t.attachEvent("onload",l))},a.render=function(){for(var n,o,r=document.querySelectorAll("img[data-echo], [data-echo-background]"),d=r.length,l={l:0-e.l,t:0-e.t,b:(t.innerHeight||document.documentElement.clientHeight)+e.b,r:(t.innerWidth||document.documentElement.clientWidth)+e.r},f=0;d>f;f++)o=r[f],i(o,l)?(c&&o.setAttribute("data-echo-placeholder",o.src),null!==o.getAttribute("data-echo-background")?o.style.backgroundImage="url("+o.getAttribute("data-echo-background")+")":o.src=o.getAttribute("data-echo"),c||(o.removeAttribute("data-echo"),o.removeAttribute("data-echo-background")),u(o,"load")):c&&(n=o.getAttribute("data-echo-placeholder"))&&(null!==o.getAttribute("data-echo-background")?o.style.backgroundImage="url("+n+")":o.src=n,o.removeAttribute("data-echo-placeholder"),u(o,"unload"));d||a.detach()},a.detach=function(){document.removeEventListener?t.removeEventListener("scroll",l):t.detachEvent("onscroll",l),clearTimeout(n)},a});
+!function(t,e){"function"==typeof define&&define.amd?define(function(){return e(t)}):"object"==typeof exports?module.exports=e:t.echo=e(t)}(this,function(t){"use strict";var e,n,o,r,c,a={},u=function(){},d=function(t){return null===t.offsetParent},l=function(t,e){if(d(t))return!1;var n=t.getBoundingClientRect();return n.right>=e.l&&n.bottom>=e.t&&n.left<=e.r&&n.top<=e.b},i=function(){(r||!n)&&(clearTimeout(n),n=setTimeout(function(){a.render(),n=null},o))};return a.init=function(n){n=n||{};var d=n.offset||0,l=n.offsetVertical||d,f=n.offsetHorizontal||d,s=function(t,e){return parseInt(t||e,10)};e={t:s(n.offsetTop,l),b:s(n.offsetBottom,l),l:s(n.offsetLeft,f),r:s(n.offsetRight,f)},o=s(n.throttle,250),r=n.debounce!==!1,c=!!n.unload,u=n.callback||u,a.render(),document.addEventListener?(t.addEventListener("scroll",i,!1),t.addEventListener("load",i,!1)):(t.attachEvent("onscroll",i),t.attachEvent("onload",i))},a.render=function(n){for(var o,r,d=(n||document).querySelectorAll("[data-echo], [data-echo-background]"),i=d.length,f={l:0-e.l,t:0-e.t,b:(t.innerHeight||document.documentElement.clientHeight)+e.b,r:(t.innerWidth||document.documentElement.clientWidth)+e.r},s=0;i>s;s++)r=d[s],l(r,f)?(c&&r.setAttribute("data-echo-placeholder",r.src),null!==r.getAttribute("data-echo-background")?r.style.backgroundImage="url("+r.getAttribute("data-echo-background")+")":r.src!==(o=r.getAttribute("data-echo"))&&(r.src=o),c||(r.removeAttribute("data-echo"),r.removeAttribute("data-echo-background")),u(r,"load")):c&&(o=r.getAttribute("data-echo-placeholder"))&&(null!==r.getAttribute("data-echo-background")?r.style.backgroundImage="url("+o+")":r.src=o,r.removeAttribute("data-echo-placeholder"),u(r,"unload"));i||a.detach()},a.detach=function(){document.removeEventListener?t.removeEventListener("scroll",i):t.detachEvent("onscroll",i),clearTimeout(n)},a});

src/echo.js

@@ -89,10 +89,10 @@
         }
 
         if (elem.getAttribute('data-echo-background') !== null) {
-          elem.style.backgroundImage = "url(" + elem.getAttribute('data-echo-background') + ")";
+          elem.style.backgroundImage = 'url(' + elem.getAttribute('data-echo-background') + ')';
         }
-        else {
+        else if (elem.src !== (src = elem.getAttribute('data-echo'))) {
-          elem.src = elem.getAttribute('data-echo');
+          elem.src = src;
         }
 
         if (!unload) {
@@ -105,7 +105,7 @@
       else if (unload && !!(src = elem.getAttribute('data-echo-placeholder'))) {
 
         if (elem.getAttribute('data-echo-background') !== null) {
-          elem.style.backgroundImage = "url(" + src + ")";
+          elem.style.backgroundImage = 'url(' + src + ')';
         }
         else {
           elem.src = src;