从if else转换为switch语句 [英] convert from if else to switch statement

问题描述

我有以下if，否则if，else构造，我只是好奇我如何将构造转换为switch语句。

I have the following if, else if, else construct and I am just curious how I could convert such as construct into a switch statement.

var emailSubject = email.subject.toLowerCase(); 
if(emailSubject.indexOf("account request") >= 0){
     //do acct req
}else if(emailSubject.indexOf("accounts pending removal for") >= 0){
     //do account removal 
}else if(emailSubject.indexOf("listserv application") >= 0){
     //do listserv app 
}else if(emailSubject.indexOf("student organization webmaster transfer request") >= 0){
     //do webmaster xfer 
}else{
     //do default 

} 

我的想法是，但我不认为这是正确的：

My thoughts are but I do not think this is correct:

switch(emailSubject){
    case this.indexOf("account request"):
       //do acct request 
       break;
    default:
       //do default 
}

或

switch(0){
   case emailSubject.indexOf("accounts pending removal"):
     //process account pending removal 
     break;
   default:
     //do default behavior 
}

推荐答案

您的示例代码在大多数语言中都不能轻易转换为switch语句，也不应该。 switch 用于将单个变量与一系列常量值进行比较，而您的逻辑需要与非常量值进行比较，没有变量可与之进行比较。 如果 / 否则，如果是您案件的正确结构。

Your example code cannot easily be converted to a switch statement in most languages, nor should it. switch is for comparing a single variable against a range of constant values, whereas your logic requires comparison against non-constant values, with no variable to compare them with. if/else if is the correct construction for your case.

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