JavaScript流程控制语句及函数

<script>
    //1、if
    var count = 3;
    if(count == 3){
        alert(count);
    }
</script>

<script>
    //2、switch
    var num = 3;
    switch (num){
        case 1: {
            alert("星期一");
            break;
        }
        case 2: {
            alert("星期二");
            break;
        }
        case 3: {
            alert("星期三");
            break;
        }
        case 4: {
            alert("星期四");
            break;
        }
        case 5: {
            alert("星期五");
            break;
        }
        case 6: {
            alert("星期六");
            break;
        }
        case 7: {
            alert("星期日");
            break;
        }
        default: {
            alert("输入的星期有误");
            break;
        }
    }
</script>

<script> 
   //3、for
    var sum = 0;
    for(let i = 1; i <= 100; i++){
        sum += i;
    }
    alert(sum);
</script>

<script>
   var sum = 0;
    var i = 1;
    while(i <= 100){
        sum += i;
        i++;
    }
    alert(sum);
</script>

<script>
  //5、do...while
    var sum = 0;
    var i = 1;
    do{
        sum += i;
        i++;
    }while(i <= 100);
    alert(sum);
</script>

function functionName(参数1，参数2...){
        要执行的代码
}

function add(a,b){
        return a + b;
}

let result = add(1,2);

var funtionName  = function(参数列表){
        要执行的代码
}

var add = function(a,b){
        return a + b;
}

let result = add(1,2,3）