How to specify multiple conditions in an 'if' statement in JavaScript

Question

Here is how I tried to mention two conditions if this or this, but it doesn't work.

if (Type == 2 && PageCount == 0) !! (Type == 2 && PageCount == '') {
    PageCount = document.getElementById('<%=hfPageCount.ClientID %>').value;
}

How do I specify multiple conditions in an if statement?

Isn't this question just a typo, one of the reasons for closing questions? Really curious as to why this has so many upvotes... — Ruan Mendes, Aug 04 '22 at 17:04
This question is being [discussed on Meta](https://meta.stackoverflow.com/questions/419635/questions-with-simple-syntax-errors). — EJoshuaS - Stand with Ukraine, Aug 04 '22 at 17:17

score 210 · Accepted Answer · edited Sep 09 '22 at 14:45

210

Just add them within the main bracket of the if statement like:

if ((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')) {
    PageCount = document.getElementById('<%=hfPageCount.ClientID %>').value;
}

Logically, this can be rewritten in a better way too! This has exactly the same meaning:

if (Type == 2 && (PageCount == 0 || PageCount == '')) {

edited Sep 09 '22 at 14:45

Peter Mortensen

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answered Jan 03 '12 at 09:58

AlanFoster

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score 52 · Answer 2 · edited Sep 09 '22 at 15:11

52

Here is an alternative way to do that.

const conditionsArray = [
    condition1,
    condition2,
    condition3,
]

if (conditionsArray.indexOf(false) === -1) {
    "Do something"
}

Or ES7 (or later):

if (!conditionsArray.includes(false)) {
   "Do something"
}

edited Sep 09 '22 at 15:11

Peter Mortensen

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answered Jul 27 '18 at 20:20

Glen Thompson

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1

As for me - just too complex. If there is no specific reason to do it this way I would suggest using `&&` operator and, if you do not want to write long/multi-line condition inside `if`, put this under a variable. – AndreyProgr Dec 16 '21 at 11:45
2

I really like this idea. I ran into a need to add a lot of conditions and this cut down my code a lot. Much more readable. Thanks! – Kenneth Streit Apr 05 '22 at 16:38
1

Note that this doesn't short-circuit, if you wanted to do that you would need to pass in functions and use `.findIndex` or `.find` – Samathingamajig Aug 05 '22 at 15:33

score 15 · Answer 3 · answered Oct 20 '13 at 13:53

15

I am currently checking a large number of conditions, which becomes unwieldy using the if statement method beyond say 4 conditions. Just to share a clean looking alternative for future viewers... which scales nicely, I use:

var a = 0;
var b = 0;

a += ("condition 1")? 1 : 0; b += 1;
a += ("condition 2")? 1 : 0; b += 1;
a += ("condition 3")? 1 : 0; b += 1;
a += ("condition 4")? 1 : 0; b += 1;
a += ("condition 5")? 1 : 0; b += 1;
a += ("condition 6")? 1 : 0; b += 1;
// etc etc

if(a == b) {
    //do stuff
}

answered Oct 20 '13 at 13:53

Edward Taylor

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1

I see no comments that this is unwise practice, so I think it is save to use. Thanks! – CousinCocaine Apr 17 '18 at 19:27
6

It's worth noting and mentioning that this only works if all conditions must evaluate to true. In other words, this is another way of writing `AND` but not `OR`. – Mark Kramer Nov 27 '19 at 17:04
7

This requires all conditions to be (potentially unnecessarily) evaluated - in this way it's like a very inefficient alternative to AND. – Shaedo Mar 02 '22 at 03:00
The redundancy calls for a loop of some kind (unless the conditions are totally arbitrary). – Peter Mortensen Sep 09 '22 at 14:53

score 10 · Answer 4 · edited Sep 09 '22 at 14:51

10

The whole if should be enclosed in brackets and the or operator is || and not !!, so

if ((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')) { ...

edited Sep 09 '22 at 14:51

Peter Mortensen

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answered Jan 03 '12 at 09:59

Fabrizio Calderan

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score 4 · Answer 5 · edited Sep 09 '22 at 15:08

4

Sometimes you can find tricks to further combine statements.

Like for example:

0 + 0 = 0

and

"" + 0 = 0

so

PageCount == 0
PageCount == ''

can be written like:

PageCount+0 == 0

In JavaScript, 0 is just as good as false. Inverting !, it would turn 0 into true:

!PageCount + 0

For a grand total of:

if (Type == 2 && !PageCount + 0) PageCount = elm.value;

edited Sep 09 '22 at 15:08

Peter Mortensen

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answered May 05 '14 at 23:51

user40521

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5

This is if you want to make your code as short as possible but it goes against many good practices. Keep your code readable. This answer is cryptic and will induce the next person looking at your code into making some mistake. – belvederef Aug 20 '19 at 12:51

score 4 · Answer 6 · edited Sep 09 '22 at 14:49

4

Wrap them in an extra pair of parentheses and you're good to go.

if((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == ''))
    PageCount = document.getElementById('<%=hfPageCount.ClientID %>').value;
}

edited Sep 09 '22 at 14:49

Peter Mortensen

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answered Jan 03 '12 at 09:58

Sergio Tulentsev

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score 3 · Answer 7 · edited Sep 09 '22 at 14:46

3

if((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')) {

    PageCount = document.getElementById('<%=hfPageCount.ClientID %>').value;
}

This could be one of possible solutions, so 'or' is ||, not !!.

edited Sep 09 '22 at 14:46

Peter Mortensen

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answered Jan 03 '12 at 09:58

vaske

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Gass · Answer 8 · 2022-03-27T15:35:16.873

1

In case you have to many conditions and you want to add them inside only one conditional statement, then you can add the conditions into an array and then construct the conditional statement like so:

let n = 5
let txt = 'hello'

let c = [
  n === 5, 
  n === 4, 
  n === 6,
  txt === 'hello', 
  txt === 'bye'
]

if(c[0] || c[1] || c[2] || c[3] || c[4]){
  document.write('It satisfies ONE or MORE conditions.');
}else{
  document.write('NO conditions have been satisfied.');
}

edited Mar 27 '22 at 15:35

answered Jan 03 '22 at 21:22

Gass

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Yes, that sounds better. What language feature does it take advantage of (I presume *eval* is ***not*** used somehow)? – Peter Mortensen Sep 09 '22 at 15:20

score 0 · Answer 9 · edited Sep 09 '22 at 15:12

0

OR operator

if ( con1 == True || con2 == True || con3 == True){
     // Statement ...
}

AND operator

if ( con1 == True && con2 == True && con3 == True){
     // Statement ...
}

It works on mine :D

edited Sep 09 '22 at 15:12

Peter Mortensen

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answered Sep 23 '21 at 03:54

Charls Catipay

45
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Normally you wouldn't use `con1 == True`, you'd just use `con1`. When con1 is something like `x == y`. – Peter Cordes Aug 05 '22 at 09:33
Well, given that `True` is not necessarily `true`, maybe it's a variable defined elsewhere? – General Grievance Aug 05 '22 at 13:21
Re *"It works on mine"*: Can you be more specific? For example, environment (browser (incl. version) (e.g. [Firefox](https://en.wikipedia.org/wiki/Mozilla_Firefox)), [Node.js](https://en.wikipedia.org/wiki/Node.js) (incl. version), build system (e.g. [Babel](https://en.wikipedia.org/wiki/Babel_(transcompiler))), etc.), supported ECMAScript version, etc.? Please respond by [editing (changing) your answer](https://stackoverflow.com/posts/69293829/edit), not here in comments (********* ***without*** ********** "Edit:", "Update:", or similar - the answer should appear as if it was written today). – Peter Mortensen Sep 09 '22 at 15:14

How to specify multiple conditions in an 'if' statement in JavaScript

9 Answers9

OR operator

AND operator

Linked

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