在ws中打开点击换不了背景,但是放在桌面上打开可以实现功能,该怎么修改??

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    <head>
        <meta charset="UTF-8">
        <meta name="viewport"
              content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>Document</title>
        <style>
            * {
                margin: 0;
                padding: 0;
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            body {
                background: url(img/1.jpg) no-repeat center top;
            }

            li {
                list-style: none;
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            .baidu {
                overflow: hidden;
                margin: 100px auto;
                background-color: #fff;
                width: 410px;
                padding-top: 3px;
            }

            .baidu li {
                float: left;
                margin: 0 1px;
                cursor: pointer;
            }

            .baidu img {
                width: 100px;
            }
        </style>

    </head>
    <body>
        <ul class="baidu">
            <li><img src="img/1.jpg"></li>
            <li><img src="img/2.jpg"></li>
            <li><img src="img/3.jpg"></li>
            <li><img src="img/4.jpg"></li>
        </ul>
        <script>
            var lis = document.querySelector('.baidu').querySelectorAll('img');
            for (var i = 0; i < lis.length; i++) {
                lis[i].onclick = function () {
                    console.log(this.src);
                    document.body.style.backgroundImage = 'url(' + this.src + ')';
                }
            }
        </script>
    </body>
</html>

 

"ws"是什么??