JavaScript: Simple way to check if variable is equal to two or more values? [duplicate]

This question already has an answer here:

Is there an easier way to determine if a variable is equal to a range of values, such as:

if x === 5 || 6


rather than something obtuse like:

if x === 5 || x === 6


?

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Why do you consider the latter obtuse?
– Alnitak
Aug 24 ’12 at 20:42

Because I need to write some code that checks if a variable has one of 20 values, namely, if x = “New York" || “Austin" || “Alberta", etc.
– Adam Templeton
Aug 24 ’12 at 20:56

@AdamTempleton: Either put all your values in an array, and then use indexOf, or you can also use a regex /^(New York|Austin|Alberta)$/.test(x).
– João Silva
Aug 24 ’12 at 21:02

indexOf

/^(New York|Austin|Alberta)$/.test(x)

@AdamTempleton in which case you should rewrite your question to say so. You specifically say two in the subject.
– Alnitak
Aug 24 ’12 at 22:32

Use s = new Set([5, 6]); s.has(x);. Not sure why I can’t anser this question.
– Denly
Jan 9 at 6:27

8 Answers
8

You can stash your values inside an array and check whether the variable exists in the array by using .indexOf:

.indexOf

if([5, 6].indexOf(x) > -1) {
// ...
}


If -1 is returned then the variable doesn’t exist in the array.

-1

This does not work in IE < 9. See MDN’s Array#indexOf Compatibility section for code that you can insert to actually make it work in IE. However, unless you are using this in several places, it would probably be faster just to use a == 1 || a == 2.
– Reid
Aug 24 ’12 at 21:55

a == 1 || a == 2

Alternatively, if you are using a JS framework, both MooTools and Prototype ensure Array#indexOf exists. jQuery, on the other hand, provides its own implementation in the form of $.inArray. I’m not familiar with any other frameworks, but I’m sure they all include such functionality in some manner.
– Reid
Aug 24 ’12 at 22:00

$.inArray

A bit more description of the code would have been nice.
– Julix
Oct 14 ’16 at 0:38

Depends on what sort of test you’re performing. If you’ve got static strings, this is very easy to check via regular expressions:

if (/^[56ab]$/.test(item)) {
//-or-
if (/^(foo|bar|baz|fizz|buzz)$/.test(item)) {
doStuff();
} else {
doOtherStuff();
}


If you’ve got a small set of values (string or number), you can use a switch:

switch

switch (item) {
case 1:
case 2:
case 3:
doStuff();
break;
default:
doOtherStuff();
break;
}


If you’ve got a long list of values, you should probably use an array with ~arr.indexOf(item), or arr.contains(item):

~arr.indexOf(item)

arr.contains(item)

vals = [1,3,18,3902,...];
if (~vals.indexOf(item)) {
doStuff();
} else {
doOtherStuff();
}


_{Unfortunately Array.prototype.indexOf isn’t supported in some browsers. Fortunately a polyfill is available. If you’re going through the trouble of polyfilling Array.prototype.indexOf, you might as well add Array.prototype.contains.}

Array.prototype.indexOf

Array.prototype.indexOf

Array.prototype.contains

Depending on how you’re associating data, you could store a dynamic list of strings within an object as a map to other relevant information:

var map = {
foo: bar,
fizz: buzz
}
if (item in map) {
//-or-
if (map.hasOwnProperty(item)) {
doStuff(map[item]);
} else {
doOtherStuff();
}


_{in will check the entire prototype chain while Object.prototype.hasOwnProperty will only check the object, so be aware that they are different.}

in

Object.prototype.hasOwnProperty

It’s perfectly fine. If you have a longer list of values, perhaps you can use the following instead:

if ([5,6,7,8].indexOf(x) > -1) {
}


Sorry. Yoshi’s answer was much better.
– psr
Aug 24 ’12 at 21:40

Yes. You can use your own function. This example uses .some:

.some

var foo = [ 5, 6 ].some(function(val) {
return val === x;
});

foo; // true


Gave you an upvote for .some, which I’d never seen before!
– Adam Templeton
Aug 24 ’12 at 21:20

I think .some is only IE9 or up.
– Graeck
Apr 16 ’14 at 23:52

This is what I’ve decided to use:

Object.prototype.isin = function() {
for(var i = arguments.length; i--;) {
var a = arguments[i];
if(a.constructor === Array) {
for(var j = a.length; j--;)
if(a[j] == this) return true;
}
else if(a == this) return true;
}
return false;
}


You would use it like this:

var fav = 'pear',
fruit = ['apple', 'banana', 'orange', 'pear'],
plu = [4152, 4231, 3030, 4409];

if (fav.isin(fruit, plu, 'eggs', 'cheese')) {
//do something cool
}


The advantages are:

If you don’t want to allow type coercion (indexOf does not), change the two == to ===. As it stands:

indexOf

==

===

fav = "4231";
plu.indexOf(fav) //-1
fav.isin(plu) //true


no, there might be a few tricks that are case specific but in general i write code like this:

if (someVariable === 1 ||
someVariable === 2 ||
someVariable === 7 ||
someVariable === 12 ||
someVariable === 14 ||
someVariable === 19) {

doStuff();
moreStuff();

} else {
differentStuff();
}


There is one || to much after 19
– Felix Dombek
Aug 24 ’12 at 21:10

||

19

The simple answer is no. You can use a switch statement, which is easier to read if you are comparing a lot of string values, but using it for two values wouldn’t look any better.

[Edit] this seems to work, but as Dan pointed out, it is actually a false positive. Do not use this method. I leave it here for educational purposes.

Easiest way I know :

a = [1,2,3,4,5];

if(3 in a) alert("true"); // will alert true


Tested in Chrome console. Not sure if it works in other browsers.

That example works by accident. Try 3 in [1, 3] – it will return false because there is no element with the index 3 in the array [1, 3]. For that matter, 3 in ['a', 'b', 'c', 'd'] will return true.
– Dan Dascalescu
Sep 10 ’15 at 11:21

3 in [1, 3]

false

[1, 3]

3 in ['a', 'b', 'c', 'd']

Damn, so it’s a false positive. Thanks for that.
– Jeremy Thille
Sep 10 ’15 at 15:46