Real-time loading of js images provides webpage opening speed _ javascript skills

There is no need to load all the images at the beginning, so that the speed of opening the network is greatly improved. Here is a good idea. You can look at the large websites, in particular, when there are many pictures, such as large e-commerce websites, you will find that the pictures are loaded only when you scroll down the first screen, there is no need to load all the images at the beginning, which improves the speed of opening the network. The following are the ideas that I have come up with. If you have a better idea, I hope you can give me some advice.

In fact, the idea of loading images in real time is very simple. When loading a page at the beginning, you can see images that do not need to be loaded at the very beginning (for example, images below the second screen must be rolled down, it is better to set them to scroll down and load them in real time) path to a custom property, such as:, src = "http://ctc.qzonestyle.gtimg.cn/ac/ B .gif" is a 1px * 1px transparent GIF image, the "http://y3.ifengimg.com/a/2014_37/03c4830691a6d8b.jpg" in the custom property data-src is the path of the image. When you scroll down to it, replace the value in data-src with the value of src, then, remove the data-src attribute ......

The following is a demo.

 Real-time loading of js Images
Http://www.cnblogs.com/xiaomou2014cont2
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Script // compatible with IE for getElementsByClassNameif (navigator. appName = 'Microsoft Internet Explorer ') {document. getElementsByClassName = function () {var tTagName = "*"; if (arguments. length> 1) {tTagName = arguments [1];} if (arguments. length> 2) {var pObj = arguments [2]} else {var pObj = document;} var objArr = pObj. getElementsByTagName (tTagName); var tRObj = new Array (); for (var I = 0; I <objArr. length; I ++) {if (objArr [I]. className = arguments [0]) {tRObj. push (objArr [I]) ;}} return tRObj ;}// image loading function loadImg (imgClass, imgSrc) {/data-src: path for storing the image to be loaded var arrImg = document. getElementsByClassName (imgClass); // The image Array window whose class is imgClass needs to be loaded in real time. onscroll = function () {for (var I = 0; iarrImg [I]. offsetTop) {arrImg [I]. setAttribute ("src", arrImg [I]. getAttribute (imgSrc); arrImg [I]. removeAttribute (imgSrc) ;}}} loadImg ("aimg", "data-src"); script

The images in cont1 in the demo are displayed as soon as the page is loaded, and the homepage layout is fixed. You can confirm that the images are under the second screen, but for the content page, the position of the image in the subject content container is uncontrollable. This requires you to determine whether the image is within the visible range after loading the real page, if it is loaded within the visible range (of course, the home page can do the same, but if the network speed is slow, when you open the home page, you need to wait until the entire page architecture is loaded to display the image, instead of loading it from top to bottom.) You need to set the width and height attributes for the image, this allows it to take a place on the page, otherwise it will only take the size of the transparent GIF image before loading.

The following demo makes some modifications to the content page. loading is triggered during window. onload and window. onscroll.

 Real-time loading of js Images
Http://www.cnblogs.com/xiaomou2014
19-year-old girl with advanced cancer who had been cut off 7 years ago
Http://www.cnblogs.com/xiaomou2014
Http://www.cnblogs.com/xiaomou2014
Http://www.cnblogs.com/xiaomou2014
19-year-old girl with advanced cancer who had been cut off 7 years ago
19-year-old girl with advanced cancer who had been cut off 7 years ago
19-year-old girl with advanced cancer who had been cut off 7 years ago
19-year-old girl with advanced cancer who had been cut off 7 years ago
19-year-old girl with advanced cancer who had been cut off 7 years ago
Script // compatible with IE for getElementsByClassNameif (navigator. appName = 'Microsoft Internet Explorer ') {document. getElementsByClassName = function () {var tTagName = "*"; if (arguments. length> 1) {tTagName = arguments [1];} if (arguments. length> 2) {var pObj = arguments [2]} else {var pObj = document;} var objArr = pObj. getElementsByTagName (tTagName); var tRObj = new Array (); for (var I = 0; I <objArr. length; I ++) {if (objArr [I]. className = arguments [0]) {tRObj. push (objArr [I]) ;}} return tRObj ;}// image loading function loadImg (imgClass, imgSrc) {/data-src: path for storing the image to be loaded var arrImg = document. getElementsByClassName (imgClass); // The Image array whose class is imgClass needs to be loaded in real time for (var I = 0; iarrImg [I]. offsetTop) {arrImg [I]. setAttribute ("src", arrImg [I]. getAttribute (imgSrc); arrImg [I]. removeAttribute (imgSrc) ;}} window. onload = window. onscroll = function () {loadImg ("aimg", "data-src")} script