How to reduce multiple OR conditions in if statement in JavaScript?

Question

I have a condition:

if (item == 'a' || item == 'b' || item == 'c' || item == 'd' || item == 'e') {
    // statements
}

How can I reduce the branching? Is there any other way to write this in JavaScript.

Can use switch. https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/switch — Swaraj Giri, Sep 01 '16 at 05:09
Here is a good post I think might already answer your question http://stackoverflow.com/questions/2430000/determine-if-string-is-in-list-in-javascript — Steven Swait, Sep 01 '16 at 05:10

Rob M. · Accepted Answer · 2016-09-01T05:22:05.897

7

You can also use the newer Array.includes

if (['a','b','c','d','e'].includes(item)) {
  ...
}

Another option (for the very specific case you posted) would be to compare unicode point values using </>

if (item >= 'a' && item <= 'e') {
   ...
}

edited Sep 01 '16 at 05:22

answered Sep 01 '16 at 05:11

Rob M.

1

Word of caution, `Array.includes` is not supported on [IE11 or Edge](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Browser_compatibility) although a [polyfill](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Polyfill) can include it. – tresf Sep 01 '16 at 05:27
@QZSupport Array.includes is actually [supported in Edge](https://developer.microsoft.com/en-us/microsoft-edge/platform/status/arrayprototypeincludeses2016/?q=includes) (not in IE11 though). Thanks for noting that! :) – Rob M. Sep 01 '16 at 05:30
thanks, [updated](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Browser_compatibility). – tresf Sep 01 '16 at 05:37

score 5 · Answer 2 · answered Sep 01 '16 at 05:10

5

Use Array#indexOf method with an array.

if(['a','b','c','d','e'].indexOf(item) > -1){
   //.........statements......
}

answered Sep 01 '16 at 05:10

Pranav C Balan

It does reduce the code length but not the branching at all. – Kaiido Sep 01 '16 at 05:16

Nikhilesh K V · Answer 3 · 2016-09-01T05:25:48.170

3

You can use an array as shown below.

var arr = ['a','b','c','d','e'];
if(arr.indexOf(item) > -1) 
{
   //statements
}

edited Sep 01 '16 at 05:25

answered Sep 01 '16 at 05:10

Nikhilesh K V

Max · Answer 4 · 2016-09-01T05:28:20.017

2

This would work nicely:

if('abcde'.indexOf(item) > -1) {
    ...
}

You could also use the newer String.prototype.includes(), supported in ES6.

if('abcde'.includes(item)) {
    ...
}

edited Sep 01 '16 at 05:28

answered Sep 01 '16 at 05:21

Max

if item is `ab` ? – Pranav C Balan Sep 01 '16 at 05:34
@PranavCBalan If it's `ab`, he'll use your answer. His example doesn't show `ab` so I would assume he doesn't require that functionality. kk :D – Max Sep 01 '16 at 05:37

4 Answers4