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从if else转换为switch语句

switch-statement if-statement javascript

Chris · 技术社区 · 14 年前

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 

}

我的想法是正确的,但我不认为这是正确的:

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

或者

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

6 回复 | 直到 14 年前

JSBÕ±Õ¸Õ£Õ¹ 14 年前

在大多数语言中,您的示例代码不能轻松地转换为switch语句,也不应该转换为switch语句。 switch if / else if 是你案子的正确结构。

fredley 14 年前

只能使用case检查值:

switch(emailSubject){
    case "Subject1": //(emailSubject == "Subject1")
       //do acct request 
       break;
    case "Subject2": //(emailSubject == "Subject2")
       //do something else
       break;
    default:
       //do default 
}

否则应该使用if/else

joshperry 14 年前

像这样的构造通常需要多态性。。。

http://jsbin.com/utilu4/3

var mailHandlers = [

  {
    CanHandleEmail : function(email) {
      return email.subject.toLowerCase().indexOf("account request") >= 0;
    },

    HandleEmail : function(email) {
      alert("do acct req");
    }
  },

  {
    CanHandleEmail : function(email) {
      return email.subject.toLowerCase().indexOf("account pending removal for") >= 0;
    },

    HandleEmail : function(email) {
      alert("do account removal");
    }
  },

  {
    CanHandleEmail : function(email) {
      return email.subject.toLowerCase().indexOf("listserv application") >= 0;
    },

    HandleEmail : function(email) {
      alert("do listserv app");
    }
  },

  {
    CanHandleEmail : function(email) {
      return email.subject.toLowerCase().indexOf("student organization webmaster transfer request") >= 0;
    },

    HandleEmail : function(email) {
      alert("do webmaster xfer");
    }
  },

  {
    CanHandleEmail : function(email) {
      return true;
    },

    HandleEmail : function(email) {
      alert("do default");
    }
  }
];

function HandleEmail(email) {
  for(i=0; i< mailHandlers.length; i++) {
    if(mailHandlers[i].CanHandleEmail(email)){
      mailHandlers[i].HandleEmail(email);
      break;
    }
  }
};

sje397 14 年前

如前所述,if/else最适合你所拥有的。

但是,如果您要查找实际的整个主题行,而不是主题行中的单词,则可以执行以下操作:

var a = ["account request", "listserv application", "student organization webmaster transfer request"];
switch(a.indexOf(emailSubject)) {
  // ...
}

fb55 14 年前

Rawling isekaijin 9 年前

我刚在野外遇到这个,我忍不住要分享,但是 别这么做 .

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