JavaScript switch case 的用法实例[范围]

复制代码 代码如下:

function case1(num){
switch(num){
case 1:
document.writeln("show 1!!");
break;
case 2:
document.writeln("show 2!!");
break;
case 3:
document.writeln("show 3!!");
break;
default:
document.writeln("show others!!");
break;
}
}
function case2(num){
switch(num){
case 1:
document.writeln("show 1!!");
//沒有break，所以會繼續執行case 2
case 2:
document.writeln("show 2!!");
break;
case 3:
document.writeln("show 3!!");
//沒有break，所以會繼續執行case 4
case 4:
document.writeln("show 4!!");
break;
default:
document.writeln("show others!!");
break;
}
}
function case3(num){
switch(num){
case 1:
case 2:
//相當於if(num==1 || num==2)
document.writeln("show 1 or 2!!");
break;
case 3:
case 4:
//相當於if(num==3 || num==4)
document.writeln("show 3 or 4!!");
break;
default:
//相當於else
document.writeln("show others!!");
break;
}
}
function case4(num){
switch(f(num)){
case 1:
case 2:
//相當於if(num==1 || num==2)
document.writeln("show 1 or 2!!");
break;
case 3:
case 4:
//相當於if(num==3 || num==4)
document.writeln("show 3 or 4!!");
break;
default:
//相當於else
document.writeln("show others!!");
break;
}
}
function f(num){
return num;
}
function case5(num){
switch(num<=2){
case true:
document.writeln("num <= 2");
break;
case false:
document.writeln("num > 2");
break;
}
}

<script> var x=10 switch(true){ case x>0&&x<10: alert(1); break; case x>=10&&x<20: alert(2); break; } </script>
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]