case 穿透1

<input type="text" id="txt"/>
<input type="button" value="点击" id="btn"/>
<script>
/*输入月份，显示当月的天数*/

btn.onclick = function(){
    var month = txt.value;
    switch(month){
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            console.log('本月为31天');
            break;
        case 2:
            console.log('本月为28天');
            break;
        case 4:
        case 6:
        case 9:
        case 11:
            console.log('本月为30天');
            break;
        default:
            alert('宝贝你输入错误了')

    }
}
</script>