Better method of checking a bunch of conditions

Question

I'm new to javascript and still coming to terms with the language's nuances.

I have a piece of code where I have to check a set of conditions on a particular variable.

if (a=="MAIN_DOMAINNAME" || a=="DOMAIN_SERIAL" || a=="DOMAIN_REFRESH" || a=="DOMAIN_RETRY" || a=="DOMAIN_EXPIRE" || a=="DOMAIN_NEGTTL" || a=="MAIN_NS") {

Is there a better way to do this conditional check, like say:

if a is one of ("DOMAIN_SERIAL", "MAIN_DOMAINNAME", "DOMAIN_REFRESH" ) {?

score 13 · Accepted Answer · answered Jul 26 '13 at 12:57

13

Assuming a relatively modern browser, you can use Array.indexOf (spec)

if (["DOMAIN_SERIAL", "MAIN_DOMAINNAME", "DOMAIN_REFRESH"].indexOf(a) !== -1)

Note - you can easily shim it for older browsers (see the mdn link on how).

answered Jul 26 '13 at 12:57

Benjamin Gruenbaum

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8 upvotes within a minute for such a trivial answer O_o (and none on the question). – Rob W Jul 26 '13 at 12:58
@RobW What can I say? Simpler questions help more users in SO than more complicated and specific ones. If it makes you feel any better I have some answers that are 5 pages long and cite new concepts from multiple recent articles - I guess not many people found stuff like [this](http://stackoverflow.com/a/15648868/1348195) helpful. – Benjamin Gruenbaum Jul 26 '13 at 12:59

score 2 · Answer 2 · answered Jul 26 '13 at 12:58

2

A regex would be shorter and works everywhere :

if ( /^(MAIN_DOMAINNAME|DOMAIN_SERIAL|DOMAIN_REFRESH|..)$/.test(a) ) {
   // do stuff
}

FIDDLE

answered Jul 26 '13 at 12:58

adeneo

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This is not equivalent. Don't forget the ^ and $. – Rob W Jul 26 '13 at 12:59

score 1 · Answer 3 · answered Jul 26 '13 at 12:58

1

var ars = ["DOMAIN_SERIAL", "MAIN_DOMAINNAME", "DOMAIN_REFRESH"];
if(ars.some(function(ar){ return a === ar; })){
     // do smth
}

answered Jul 26 '13 at 12:58

karaxuna

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estrar · Answer 4 · 2013-07-26T14:24:16.063

1

Should mention the switch statement as it should be working fine with the example given in the question.

switch(a) {
  case('MAIN_DOMAINAME'):
  case('DOMAIN_SERIAL'):
  case('DOMAIN_REFRESH'):
  case('DOMAIN_RETRY'):
    console.log('Go wild.');
  break;
}

Not as lightweight as the other answers, but it's readable and matches (a === b).

edited Jul 26 '13 at 14:24

answered Jul 26 '13 at 13:38

estrar

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score 0 · Answer 5 · answered Jul 26 '13 at 13:16

I prefer the regex solution already provided by adeneo, but if you want something that matches the

if a is one of (...

wording from the question reasonably closely you can do this:

if (a in list("MAIN_DOMAINNAME", "DOMAIN_SERIAL", "DOMAIN_REFRESH", "DOMAIN_RETRY")) {
    // do something                 (rest of list omitted to avoid scrolling)
}

by providing a helper function to turn the list into an object:

function list() {
   var o={}, i;
   for (i=0; i < arguments.length; i++) o[arguments[i]] = true;
   return o;
}

Of course you can omit the helper function and just use an object literal, but that's ugly:

if (a in {"MAIN_DOMAINNAME":1, "DOMAIN_SERIAL":1, "DOMAIN_REFRESH":1}) {

Better method of checking a bunch of conditions

5 Answers5