一、前端基础-JavaScript-JavaScript控制语句

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<!-- 控制语句
    1、if
    2、switch
    3、for:和python有区别，循环默认打印位置（下标）
    4、while
-->

<!-- if 语句 -->
<script>
    var a = 1;
    if (a === 1){
        alert(1)
    }else if (a === 2){
        alert(2)
    }else {
        alert(false)
    }
</script>

<!-- switch -->
<script>
    var k = 3;
    switch (k){
        case 1:v=1;break;
        case 2:v=2;break;
        case 3:v=3;break;
        default:y=111;
    }
    alert(v)
</script>

<!-- for循环 -->
<script>
    var l = [1,'aaa',true];
    //对比python
    for (var i in l){
        alert(i);
        alert(l[i]) //打印列表的值
    }

    //格式 初始值；结束条件；循环操作
    for (var j = 1;j < 10;j=i+1){
        alert(j)
    }

    //for 循环求1到100的和
    var ret = 0;
    for (var c =1;c < 101;c =c+1){
        ret = ret +c
    }
    alert(ret);

    //while 循环
    var ret1 = 0;
    var d = 0;
    while (d < 101){
        ret1= ret1 +d;
        d = d+1;
    }
    alert(ret1)
</script>
</body>
</html>