Search a named array in javascript

Question

This might be a duplicate but I could not help but post this, I have an array with this format

answerCollection= {
0:
{selected : a,
 status :  false   
 },
1:
{selected : a,
 status :  false   
 }
}

I want to do an index check on the this aray like this

if(answerCollection.indexOf(indexNo) == -1){
 sel = "a";
 }

but it keeps failing i.e. I keep getting a return value of -1, irrespectively of if the index exist in the array or not.

How do I do this kind of search?

Seems like answerCollection is a plain object instead of array. Also, the argument for indexOf is the value and not the key. — Fabrício Matté
– Fabrício Matté, Commented Jun 4, 2013 at 14:18
What happens if you do if (!answerCollection[indexNo]) { ... }? — Lloyd
– Lloyd, Commented Jun 4, 2013 at 14:19
@Lloyd I passed it to a var to check, I keep getting -1 on it — kolexinfos
– kolexinfos, Commented Jun 4, 2013 at 14:20

Khanh TO · Accepted Answer · 2013-06-04 14:32:52Z

2

if(indexNo in answerCollection){
 sel = "a";
 }

Best practice to detect properties in an object. In your case, maybe you need to convert to string

if(indexNo.toString() in answerCollection){
     sel = "a";
     }

answered Jun 4, 2013 at 14:21

Khanh TO

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1 Comment

Probably right, but explain what it does (or link to docs) to avoid confusion!

WhyMe · Accepted Answer · 2013-06-04 14:32:24Z

0

if(answerCollection[indexNo] == null){
 sel = "a";
}

for example look here.

answered Jun 4, 2013 at 14:20

WhyMe

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@Lloyd null coerces to undefined. undefined can be shadowed, null can't. null is shorter to type and in file size.

@FabrícioMatté Yes I forgot about that :)

Oh no problem. Since we're nitpicking, I'd go with if (!answerCollection[indexNo]) =]

:) I prefer my null, since I defined the collection.