文章目录

流程控制分支结构导读


if案例

    <script>
        var age = prompt('请输入年龄：');
        if(age>=18){
   
            alert('可以进入');
        }
    </script>

三元表达式

条件表达式 ？表达式1 ：表达式2

switch

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>if</title>
    <script>
        switch(2){
   
            case 1:
            console.log('这是1');
            break;
            case 2:
            console.log('这是2');
            break;
            case 3:
            console.log('这是3');    
            break;
            default:
            console.log('没有结果');
        }
    </script>
</head>
<body>
    
</body>
</html>

买水果案例

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>水果</title>
    <script>
        var fruit = prompt('please input the type of the fruit:');
        switch(fruit){
   
            case 'apple':
            alert('$3.5');
            break;
            case 'banana':
            alert('$4.0');
            break;
            case 'peach':
            alert('$2.7');    
            break;
            default:
            alert('sold out');
        }
    </script>
</head>
<body>
    
</body>
</html>

switch与if区别