Checking string like boolean

Question

I have below set of code -

if(!obj.Substance){
 ...Some Code...
}

In this condition Substance variable is of string type.

I want to check on which condition code will enter within if block? I tried setting Substance value as undefined , blank = empty string also tried to put some value. But code did not entered in if block.

Can you give an actual [mre]? It's not clear what `blank` is but both `undefined` and an empty string `''` are false-y. — jonrsharpe, Nov 14 '22 at 15:09
@jonrsharpe setting empty or undefined I tried , but its not entering within if block — C Sharper, Nov 14 '22 at 15:10
No, an _actual MRE_. Also what does this have to do with [tag:jquery] or [tag:reactjs]? — jonrsharpe, Nov 14 '22 at 15:11
Code works fine: https://jsfiddle.net/Lbw6f4dr/ must be what you're passing in, which you didn't provide. See [mcve]. — freedomn-m, Nov 14 '22 at 15:18

score 1 · Accepted Answer · answered Nov 14 '22 at 15:11

1

The code will only enter the if block if the obj.Substance variable is falsey.

The following values are falsey:

false
0
"" (empty string)
null
undefined
NaN

So, if obj.Substance is any of those values, the code will enter the if block.

answered Nov 14 '22 at 15:11

Igor

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Checking string like boolean

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