手寫Web圖片懶加載~
廢話不多說，直接上代碼：
1 <!DOCTYPE html>
2 <html>
3 <head>
4 <title>圖片懶加載</title>
5 </head>
6 <body class="body__wrap">
7 <img class="img-item" data-src="https://ss0.baidu.com/94o3dSag_xI4khGko9WTAnF6hhy/zhidao/pic/item/b2de9c82d158ccbf24cbdbd11fd8bc3eb03541e1.jpg"/>
8 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.58cdn.com.cn%2Fenterprise%2Fappearance%2Fbig%2Fn_v23adc7f847e544e69b79ec9aecee3cfbc.jpg&refer=http%3A%2F%2Fpic1.58cdn.com.cn&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=b5a8638474a8fc7a6c32ce0033d085eb"/>
9 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2F5b0988e595225.cdn.sohucs.com%2Fimages%2F20171223%2F6bb0ded3ce1a454ba03f1bdec2f3a21e.jpeg&refer=http%3A%2F%2F5b0988e595225.cdn.sohucs.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=b670fa670c8cbb6eb202ce6a6c8fe6e2"/>
10 <img class="img-item" data-src="https://img1.baidu.com/it/u=300787145,1214060415&fm=253&fmt=auto&app=138&f=JPEG?w=800&h=500"/>
11 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fimg.zhux2.com%2Feditor1557461334164035.jpg&refer=http%3A%2F%2Fimg.zhux2.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257937&t=b42101a51b60d03181f21fe55ccb08bd"/>
12 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fb1-q.mafengwo.net%2Fs10%2FM00%2FE2%2FAF%2FwKgBZ1kbqwOAH1MAABy3rpak-sc216.png&refer=http%3A%2F%2Fb1-q.mafengwo.net&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=0dd6850ebc0b1feec9758812b9869b1f"/>
13 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fwww.cneo.com.cn%2Fdata%2Fattachment%2Fportal%2F201906%2F26%2F162658zehn728jpqj9v2v2.jpeg&refer=http%3A%2F%2Fwww.cneo.com.cn&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=05545ba34edf07da7d7baf0df7050972"/>
14 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.58cdn.com.cn%2Fenterprise%2Fappearance%2Fbig%2Fn_v21015771e1c78477499d839e7c51ac82b.jpg&refer=http%3A%2F%2Fpic1.58cdn.com.cn&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=b8b76cb66951e23f38b55546d669b308"/>
15 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fimg.ui.cn%2Fdata%2Ffile%2F9%2F0%2F4%2F2335409.gif&refer=http%3A%2F%2Fimg.ui.cn&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=64f6e827fa1f3cc5dbd0bf61117f7c5b"/>
16 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fimg.zhux2.com%2Feditor1555854991695607.jpg&refer=http%3A%2F%2Fimg.zhux2.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=4c45b0899ec6c04f4211a1cae5769074"/>
17 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fimg.zhux2.com%2Feditor1558079251358240.jpg&refer=http%3A%2F%2Fimg.zhux2.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=c959cc1a2c2b7568d972bc81c9b2c0bc"/>
18 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.58cdn.com.cn%2Fuserauth%2Fpp%2Fn_v26f7c146e8e584f81b2b962cf89af1059.jpg&refer=http%3A%2F%2Fpic1.58cdn.com.cn&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=38db972617be1a8fc42c43a2a77b75f5"/>
19 <img class="img-item" data-src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.58cdn.com.cn%2Fenterprise%2Fappearance%2Fbig%2Fn_s12407540124093488123.jpg&refer=http%3A%2F%2Fpic1.58cdn.com.cn&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1652257964&t=3cd33543a4c96b15ad71a4456727231a"/>
20 </body>
21 <style>
22 .body__wrap {
23 height: 100vh;
24 width: 100vw;
25 }
26 .img-item {
27 width: 20vw;
28 height: 30vh;
29 display: block;
30 }
31 </style>
32 <script>
33 function lazyLoadImage() {
34 const imgs = document.getElementsByTagName('img');
35 for(img of imgs) {
36 const rande = img.getBoundingClientRect&&img.getBoundingClientRect();
37 if(rande&&(rande.top+30)<window.innerHeight) {
38 img.src = img.dataset.src;
39 } else {
40 break
41 }
42 }
43 }
44
45 window.addEventListener('scroll', lazyLoadImage)
46 lazyLoadImage()
47 </script>
48 </html>
我們可以根據此思路去拓展我懶加載的功能，例如：圖片加載失敗，圖片加載中的狀態，默認展示的圖片等等。
拿Vue組件封裝舉例，將需要懶加載的圖片放置在當前組件容器中，然后走上面的邏輯代碼，拿到所有圖片，或者不需要懶加載的地方可以設置data-lazy=false,等等，具體需要什么看你自己的拓展！
拜拜~
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