JavaScript: Can I declare variables inside switch cases? [duplicate]

Question

In C language, you cannot declare any variables inside 'case' statements.

switch ( i ){
case 1:
  int a = 1; //error!
  break;
}

However, you can when you use with curly parentheses.

switch ( i ){
case 1:
  {// create another scope.
    int a = 1; //this is OK.
  }
  break;
}

In Javascript case, can I use var directly inside case statements?

switch ( i ){
case 1:
  var a = 1
  break
}

It seems that there is no error but I'm not confident this is grammatically OK.

javascript es5 only has function scope, a will be local to the function, not to the switch — Hacketo
– Hacketo, Commented Sep 18, 2015 at 8:25
@Hacketo So, Javascript can only have scopes within the global and functions? — PRIX
– PRIX, Commented Sep 18, 2015 at 8:39
@PRIX using var, yes. you can see many examples in the linked post — Hacketo
– Hacketo, Commented Sep 18, 2015 at 8:43
Note that you cannot declare the same variable in different cases because there is only one underlying block. — Franklin Yu
– Franklin Yu, Commented Dec 28, 2016 at 3:58

Ashkan Mobayen Khiabani · Accepted Answer · 2020-01-14 18:11:52Z

8

Yes in javascript you can do this but I think testing it would be much simpler:

var i = 1;
switch ( i ){
case 1:
  var a = 1;
  alert(a);
  break;
}

answered Sep 18, 2015 at 8:30

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