3.JS

代码：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<button onclick=alert("谁让你点的")>别点</button>
<button id="id1">点开吧</button>
<script>
    document.getElementById('id1').onclick=function () {
        alert("让你点你就点啊");
    }
</script>
</body>
</html>

即可

代码：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var name="devops
linux" ;
    var age=18;
    var gender=true;
    console.log(name);
    console.log(typeof (name));
    console.log(typeof (age));
    console.log(name.length);
    console.log(name+'
centos');
    var num1='101';
    var num2=200;
    console.log(num1+num2);
    console.log(Number(num1)+num2);
</script>
</body>
</html>

　　效果

即可

代码

    var num3=100;
    var num4=50;
    console.log(num3+num4);
    console.log(num3-num4);
    console.log(num3*num4);
    console.log(num3/num4);
    console.log(num3%num4);

    console.log(true);
    console.log(false);
    console.log(true&&true);
    console.log(true&&false);
    console.log(true||false);
    console.log(!true);

　　效果

代码：

    console.log(5>3);
    console.log(5<3);
    //==和===的区别,==只进行值比较，===类和值同时相等，则相等
    console.log(5=='5');
    console.log(5==='5');
    console.log(5===5);

代码

    var age=10;
    if(age>=18){
        console.log("已经长大");
    }else if(age<8){
        console.log("还没上小学");
    }else {
        console.log("正在长大");
    }

代码：

    var day=new Date().getDay();
    switch (day) {
        case 1:
            console.log("今天是周一");
            break;
        case 2:
            console.log("今天是周二");
            break;
        case 3:
            console.log("今天是周三");
            break;
         case 4:
            console.log("今天是周四");
            break;
         case 5:
            console.log("今天是周五");
            break;
         case 6:
            console.log("今天是周六");
            break;
         default:
            console.log("今天是周日");
            break;
    }

    for(i=1;i<5;i++){
        console.log("这是第"+i+"次");
    }

    var j=1;
    while (j<=5){
        console.log("这是第"+j+"次while");
        j++;
    }

    var k=1;
    do {
        console.log("这是第"+k+"次do while");
        k++;
    }while(k<=5)

    var h=1;
    while (h<10){
        if(h>5){
           console.log("已经超过五次") ;
           continue;
           break;
        }else {
            console.log("这是第"+h+"次continue");
        }
        j++;
    }

即可