Loding缓存展示的写法-vue3

1、缓存效果展示：
2、缓存代码编写：
<style>
        body{
            padding-bottom: 800px;
        }
        img{
            width: 400px;
            height: 400px;
            border: 1px solid #dedede;
        }
    </style>
</head>
<body>
    <!-- <img src="data:image/gif;base64,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" alt="" srcset=""> -->
    <div id="app">
        <img v-preload=" img " style="object-fit:cover">
    </div>

    <script>
        let arr = document.querySelectorAll("img[v-preload]");
        arr.forEach((dom)=>{
            // dom.src = "../assets/img/loading.gif"
            dom.src = "data:image/gif;base64,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";
            dom.tempStyle = dom.style.cssText;
            dom.style.objectFit="scale-down";
            dom.style.objectPosition="center";
        })
    </script>
    <script type="module">
        import { createApp } from "../assets/vue/3.0/vue.esm-browser.js";
        const app = createApp({
            data(){
                return {
                    img:"https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic.jj20.com%2Fup%2Fallimg%2F1112%2F11251Q24100%2F1Q125124100-5.jpg&refer=http%3A%2F%2Fpic.jj20.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1665718104&t=91a061cac8657bf9b1bc3ead30017584"
                }
            }
        })
        
        app.directive("preload", function(el,binding){
            if(binding.value==binding.oldValue) return;
            // el.src = "../assets/img/loading.gif"
            // let tempStyle = el.style.cssText;
            // el.style.objectFit="scale-down";
            // el.style.objectPosition="center";

            let imgDom = new Image();
            imgDom.src = binding.value;
            imgDom.onload = function(){
                // console.log("图片加载完成");
                el.src = binding.value;
                el.style.cssText = el.tempStyle;
            }

        })

        app.mount("#app")
    </script>
Loding缓存展示的写法-vue3

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