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javascript - 如何正确创建 LazyLoad es6 类？

问题描述

我使用此代码延迟加载图像 - https://jsbin.com/bozulobina/1/edit?html,css,js,output

function lazyLoad() {

  const lazyImages = document.querySelectorAll("img");
  const imageObserver = new IntersectionObserver((entries, observer) => {
    entries.forEach(entry => {
      if (entry.isIntersecting) {
        let image = entry.target;
        image.src = image.dataset.src;
        image.classList.remove("lazy");
        imageObserver.unobserve(image);
      }
    });
  });

  lazyImages.forEach(image => {
    imageObserver.observe(image)
  });

}
window.addEventListener('DOMContentLoaded', lazyLoad);

尝试使用 es6 类重写此代码 - https://jsbin.com/rejurobupa/1/edit?html,css,js,output

class LazyLoad{
  constructor(imgElement){
    this.imgElement = imgElement;
    this.interObserver()
  }
  interObserver() {
    const imageObserver = new IntersectionObserver((images, options) => {
      images.forEach(image => {
        if (image.isIntersecting) {
          let imageLazy = image.target;
          imageLazy.src = imageLazy.dataset.src;
          imageLazy.classList.remove(this.imgElement);
          imageObserver.unobserve(imageLazy);
        }
      });
    });

    lazyImages.forEach(image => imageObserver.observe(image));
  }  

}
const lazyImages = document.querySelectorAll("img");
const lazyLoad = new LazyLoad(lazyImages);
window.addEventListener('DOMContentLoaded', lazyLoad);

告诉我如何做正确，我在哪里犯错？

先感谢您

标签： javascripthtmlcsses6-class

解决方案

我更新了答案。更正如下：

  • 在 img 元素上设置高度和宽度
  • 在 DOMContentLoaded 上调用 LazyLoad 构造函数

class LazyLoad{
  constructor( imgClass ) {
    this.imgClass = imgClass;
    this.imgElement = document.querySelectorAll(imgClass);    
    this.interObserver();
  }
  interObserver() {
    const imageObserver = new IntersectionObserver((images, options) => {
      images.forEach(image => {
        if (image.isIntersecting) {
          let imageLazy = image.target;
          imageLazy.src = imageLazy.dataset.src;
          imageLazy.classList.remove(this.imgClass);
          imageObserver.unobserve(imageLazy);
        }
      });
    });
  
    this.imgElement.forEach(image => imageObserver.observe(image));
  }    
}

window.addEventListener('DOMContentLoaded', new LazyLoad(".lazy-img"));
img{
  display: block;
  width:300px;
  height:300px;
}
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>
  
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/animals" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/arch" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/nature" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/people" alt="">

<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/animals" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/arch" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/nature" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/people" alt="">

<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/animals" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/arch" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/nature" alt="">
<img src="#" class="lazy-img" data-src="https://placeimg.com/300/300/people" alt="">

</body>
</html>

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