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Intersection Observer image lazy loading implementation method

小云云Original: 2018-01-31 13:17:291286browse

This article mainly brings you an example of IntersectionObserver implementing lazy loading of images. The editor thinks it is quite good, so I will share it with you now and give it as a reference for everyone. Let’s follow the editor to take a look, I hope it can help everyone.

API:

https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API

Go directly to the source code:

<!DOCTYPE html>
<html>
  <header>
    <style>
      .list-item{
        height: 400px; 
        margin: 5px; 
        background-color: lightblue; 
        list-style: none;
      }
    </style>
  </header>
  <body>
    <li class="list-item"><img class="list-item-img" alt="loading" src=&#39;./images/icon1.png&#39;></li>
    <li class="list-item"><img class="list-item-img" alt="loading" src=&#39;./images/icon2.png&#39;></li>
    <li class="list-item"><img class="list-item-img" alt="loading" src=&#39;./images/icon3.png&#39;></li>
    <li class="list-item"><img class="list-item-img" alt="loading" src=&#39;./images/icon4.png&#39;></li>
    <li class="list-item"><img class="list-item-img" alt="loading" src=&#39;./images/icon5.png&#39;></li>
    <li class="list-item"><img class="list-item-img" alt="loading" src=&#39;./images/icon6.png&#39;></li>

    <script>
      var observer = new IntersectionObserver(function(changes) {
        console.log(changes);
        changes.forEach(function(element, index) {
          // statements
          if (element.intersectionRatio > 0 && element.intersectionRatio <= 1) {
            element.target.src = element.target.dataset.src;
          }
        });
      });


      function addObserver() {
        var listItems = document.querySelectorAll(&#39;.list-item-img&#39;);
        listItems.forEach(function(item) {
          observer.observe(item);
        });
      }

      addObserver();
    </script>
  </body>
</html>

After running the code, I found that when scrolling the scroll axis, only When the 25edfb22a4f469ecb59f1190150159c6 area is completely displayed, the corresponding http request to download the image will be triggered.

Compatible browsers:

desktop:

Mobile:

Related recommendations:

Use the vue-lazyload plug-in to lazily load images in vue

Lazy loading of images

JS implementation of image lazy loading tutorial

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