Javascript inoperant Switch Case with a regex

Question

It looks like the javascript switch case doesn't like the regex as a case as it works with static values but I can't get the expected answers using regex in the case statement.

Would you pls confirm that limitation of the js interpretor and propose a work around (I mean not a if-then blocks suite) ?

Thx

example (not giving the expected answer ,eg 'case3') :

<script type="text/javascript">
var testme = "pwd_foo";
var response = false;
var reg = /^pwd.+/;

switch (testme) {
case 'pwd':
    response = 'case1';
    break;
case reg.test:
    response = 'case2';
    break;
case /^pwd.+/:
   response = 'case3';
   break;
default:
    response = 'do sthg else';
}

alert('reg test: ' + reg.test(testme)+'\nresponse:' + response);
</script>

mplungjan · Accepted Answer · 2015-07-23T19:41:14.163

9

Your tests do not really lend themselves to a switch. If you must, you can do this which is NOT RECOMMENDED:

DEMO HERE

var testme = "pwd_foo", response;
var reg = /^pwd.+/;

switch (true) {
case testme=='pwd':
    response = 'case1';
    break;
case reg.test(testme):
    response = 'case2';
    break;
default:
    response = 'do sthg else';
}

alert('reg test: ' + reg.test(testme)+'\nresponse:' + response);

edited Jul 23 '15 at 19:41

answered Jul 05 '11 at 07:48

mplungjan

169,008
28
173
236

Mmmm, I remember a certain comment: http://stackoverflow.com/questions/6395171/switch-statement-in-javascript/6395203#6395203 – KooiInc Jul 05 '11 at 08:19
Haha - my past comes back to haunt me ;) Please note the "If you must" – mplungjan Jul 05 '11 at 08:31
especially for you, I added a nice ternary solution >-D – KooiInc Jul 05 '11 at 09:44
1

Non-commenting down voters should be banned ! - this has been specifically noted as a workaround, not a best practise! – mplungjan Jan 12 '13 at 05:07

score 1 · Answer 2 · edited May 23 '17 at 10:31

1

You can also use a ternary for this (but do see the disclaimer here):

var testme = "pwd_foo", 
    response = 
       testme === 'pwd' 
         ? 'case1' 
         : /^pwd.+/.test(testme) 
           ? 'case2' 
           : 'do something else';

edited May 23 '17 at 10:31

Community

1
1

answered Jul 05 '11 at 09:43

KooiInc

119,216
31
141
177

thx but that's not what I was looking for, as my question is trying to simplify the real case I need. No doubt, I need a switch case for my particular purpose. I used the switch(true) which works like a charm. – hornetbzz Jul 05 '11 at 10:07
That's ok. It's just a demonstration of an alternative and a little teaser for @mplungjan who in a previous life demonstrated an aversion for ternaries (and the `switch(true)` construction for that matter) – KooiInc Jul 05 '11 at 11:37

Javascript inoperant Switch Case with a regex

2 Answers2