<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        var age = 20 // 成年人观看
        if (age > 18){
            console.log("成年人观看")
        } else {
            console.log("未成年人观看")
        }
        var score = 65 // 及格
        if (score > 100 || score < 0) {
            console.log("数字应该在0~100之间")
        } else if (score > 90) {
            console.log("优秀")
        } else if (score > 80) {
            console.log("良好")
        } else if (score > 60){
            console.log("及格")
        } else{
            console.log("不及格")
        }
        var week = 123 // 非法输入
        switch (week){
            case 0:console.log("星期日");break
            case 1:console.log("星期一");break
            case 2:console.log("星期二");break
            case 3:console.log("星期三");break
            case 4:console.log("星期四");break
            case 5:console.log("星期五");break
            case 6:console.log("星期六");break
            default:console.log("非法输入");
        }
    </script>
</head>
<body>
<h1>welcome to JS!</h1>
</body>
</html>
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