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簡單有效的JavaScript圖片預(yù)加載效果

2019-12-11 seo達(dá)人

首先編寫一個簡單的容器：

<style>

content {

width: 600px;

height: 100vh;

overflow-y: auto;

}

content ul {

width: 100%;

}

content ul li {

width: 50%;

float: left;

margin: 20px 0;

list-style: none;

}

content ul li p {

width: 200px;

height: 200px;

overflow: hidden;

margin: 0 auto;

border: 1px solid #999999;

}

content ul li p img {

width: 100%;

display: block;

position: relative;

top: 50%;

transform: translateY(-50%);

}

</style>

<div id="content">

<ul>

</ul>

</div>

然后，編寫js代碼：

let imageArr = [{

img_url: "http://www.lexilisi.com/Uploadpth/c45cc952-dcb7-493c-a171-357d1b820b37.png",

}, {

img_url: "http://xiaobanyou.com/static/images/xby_user_3.jpg",

}, {

img_url: "http://xiaobanyou.com/static/images/xby_user_4.jpg",

}, {

img_url: "http://xiaobanyou.com/static/images/xby_user_5.jpg",

}, {

img_url: "http://xiaobanyou.com/static/images/xby_user_6.jpg",

}, {

img_url: "http://xiaobanyou.com/static/images/xby_user_799.jpg",

}];

const lazyLoad = (src) => {

//加載loading動畫

let _image = new Image();

_image.src = './loading.gif';

//加載需要展示的圖片

let image = new Image();

image.src = src;

//加載成功，將loading圖片路徑改成對應(yīng)的真實路徑

image.onload = _ => image.src = .currentTarget.src;

//加載失敗，將loading圖片路徑改成默認(rèn)圖片路徑

image.onerror = _ => _image.src = './error.png';

return _image;

}

let _content = document.getElementById('content');

let _ul = _content.getElementsByTagName('ul');

imageArr.forEach(value => {

let _li = document.createElement('li');

let _p = document.createElement('p');

let _image = lazyLoad(value.img_url);

_p.appendChild(_image);

_li.appendChild(_p);

_ul[0].appendChild(_li);

})

展示效果如圖：

每個圖片都是異步加載，加載完成后：