switch 语句用于基于不同条件执行不同动作。语法格式如下：
switch(表达式) {

case n:

代码块

break;

case n:

代码块

break;

default:

默认代码块
}
switch(表达式) {

case n:

代码块

break;

case n:

代码块

break;

default:

默认代码块
}代码解释：计算一次 switch 表达式；把表达式的值与每个 case 的值进行对比；如果存在匹配，则执行关联代码。如下：
switch (new Date().getDay()) {
case 0:

day = "星期天";

break;
case 1:

day = "星期一";

break;
case 2:

day = "星期二";

break;
case 3:

day = "星期三";

break;
case 4:

day = "星期四";

break;
case 5:

day = "星期五";

break;
case 6:

day = "星期六";
}
switch (new Date().getDay()) {
case 0:

day = "星期天";

break;
case 1:

day = "星期一";

break;
case 2:

day = "星期二";

break;
case 3:

day = "星期三";

break;
case 4:

day = "星期四";

break;
case 5:

day = "星期五";

break;
case 6:

day = "星期六";
}扩展内容 扩展内容 JavaScript中switch语句的用法总结JavaScript中switch语句的用法总结JavaScript的switch...case语句，是在开发中经常用到的，但是通常都是给定值，然后进入case分支的操作，今天来总结一些switch的其他操作。
var a = 100;
var b = NaN;
switch (true) {
case isNaN(a) || isNaN(b):

console.log('NaNNaN');

break;
case a === b:

console.log(0);

break;
case a < b:

console.log(-1);

break;
default:

console.log(1);
}

// NaNNaN
var a = 100;
var b = NaN;
switch (true) {
case isNaN(a) || isNaN(b):

console.log('NaNNaN');

break;
case a === b:

console.log(0);

break;
case a < b:

console.log(-1);

break;
default:

console.log(1);
}

// NaNNaN多case，单操作
var Animal = 'Giraffe';
switch (Animal) {
case 'Cow':
case 'Giraffe':
case 'Dog':
case 'Pig':

console.log('This animal will go on Noah\'s Ark.');

break;
case 'Dinosaur':
default:

console.log('This animal will not.');
}

// This animal will go on Noah's Ark.
var Animal = 'Giraffe';
switch (Animal) {
case 'Cow':
case 'Giraffe':
case 'Dog':
case 'Pig':

console.log('This animal will go on Noah\'s Ark.');

break;
case 'Dinosaur':
default:

console.log('This animal will not.');
}

// This animal will go on Noah's Ark.