<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body {
            font-family: "Microsoft YaHei", serif;
        }

        body, dl, dd, p, h1, h2, h3, h4, h5, h6 {
            margin: 0;
        }

        ol, ul, li {
            margin: 0;
            padding: 0;
            list-style: none;
        }

        img {
            border: none
        }
    </style>
</head>
<body>

<script>
    var a = 10;
    function fn() {
        alert(a);
        var a = 1;
        alert(a);
    }
    fn();
    alert(a);

    // un 1 10-vue-router
</script>
</body>
</html>