JavaScript switch 语句

定义和用法

switch 语句根据不同的情况执行代码块。

switch 语句是 JavaScript 的“条件”语句的一部分，用于根据不同的条件执行不同的操作。使用 switch 选择要执行的许多代码块之一。这是长的嵌套 if/else 语句的完美解决方案。

Koda na switch yana iya gudanar da wakilci. Dukansu yana iya kiyaye wurin wakilci daidai daidai da wakilci na kowa a cikin jiki. Idan ana dace, ake gudanar da koda na yauke.

Koda na switch yana iya amfani da break ko default ko kuma biyu daga su. Dukansu ana amfani:

Koda na break ya samu harshe daga koda na switch. Haka yana toka koda ake gudanarwa cikin koda da kuma ake tafiyarwa na wakilci. Idan kowa na break bai dace, ake gudanarwa koda na kowane koda a cikin switch.

Idan kowa na case bai dace, koda na default na kira yauke na ake koda da ake gudanarwa. Idan kowa na switch bai dace, ana amfani da koda na default kawai. Ɗirɗirin a yana amfani, domin yana iya taimakawa da halaye da kuma wuriwuri.

实例

Kira koda ake ake daga shirin shiyyar wakilci:

var text;
var fruits = document.getElementById("myInput").value;
switch(fruits) {
  case "Banana":
    text = "Banana is good!";
    break;
  case "Orange":
    text = "I am not a fan of orange.";
    break;
  case "Apple":
    text = "How you like them apples?";
    break;
  default:
    text = "I have never heard of that fruit...";
}

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Matafiya masu kai a cikin shafin

Tsarin

switch(expression) {
  case n:
    Koda
    break;
  case n:
    Koda
    break;
  default:
    Koda na tsarin daidai
}

Wurin gida

Gidan shirin Bayani
expression Dauka. Kira wakilci na ake wuri. Wurin wakilci ake ake yauke daidai daidai na wakilci na kasa. Idan ana dace, ake koda na yauke.

Alamafiyar nuna

Tasiri JavaScript： ECMAScript 1

Matafiya masu kai

实例

Kira wakilci na kananin sabonai na wuri day (Sunday=0, Monday=1, Tuesday=2, ...)：

var day;
switch (new Date().getDay()) {
  case 0:
    day = "Sunday";
    break;
  case 1:
    day = "Monday";
    break;
  case 2:
    day = "Tuesday";
    break;
  case 3:
    day = "Wednesday";
    break;
  case 4:
    day = "Thursday";
    break;
  case 5:
    day = "Friday";
    break;
  case 6:
    day = "Saturday";
    break;
  default:
    day = "Unknown Day";
}

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实例

如果今天既不是星期六也不是星期日，写一条默认消息：

var text;
switch (new Date().getDay()) {
  case 6:
    text = "Today is Saturday";
    break; 
  case 0:
    text = "Today is Sunday";
    break; 
  default: 
    text = "Looking forward to the Weekend";
}

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实例

有时您会希望不同的情况使用相同的代码，或者使用相同的默认值。

请注意，在本例中，case 共享相同的代码块，并且 default case 不必是 switch 块中的最后一个 case（但是，如果 default 不是 switch 块中的最后一个 case，请记住用 break 结束它）。

var text;
switch (new Date().getDay()) {
  case 1:
  case 2:
  case 3:
  default: 
    text = "Looking forward to the Weekend";
    break; 
  case 4:
  case 5:
    text = "Soon it is Weekend";
    break; 
  case 0:
  case 6:
    text = "It is Weekend";
}

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实例

根据来自提示框的用户输入，使用 switch 语句执行代码块：

var text;
var favDrink = prompt("What's your favorite cocktail drink?");
switch(favDrink) {
  case "Martini":
    text = "Excellent choice! Martini is good for your soul.";
    break;
  case "Daiquiri":
    text = "Daiquiri is my favorite too!";
    break;
  case "Cosmopolitan":
    text = "Really? Are you sure the Cosmopolitan is your favorite?";
    break;
  default:
    text = "I have never heard of that one..";
}

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相关页面

Horon JavaScript:JavaScript If...Else 语句

Horon JavaScript:JavaScript ɗanin Switch ƙurafin

Horon JavaScript:JavaScript ɗanin if/else ƙurafin

Horon JavaScript:JavaScript ɗanin break ƙurafin