JS Check property exists for number values

Question

I have used like below example to check property exists on an object.

const payload ={payment:0}

if(payload && payload.payment){
  console.log(payload.payment)
}else{
  console.log('Issue')
}

But it fails with 0 (Zero) value.

This question is about an object which has integer key and when the key value is zero most of the other answers don't work.

Have you tried it? `'payload' in payment` does work. – Florian Weimer Oct 06 '18 at 20:33 — Florian Weimer, Oct 06 '18 at 20:33
@FlorianWeimer I found `has` in `lodash` also do this. – user2473015 Oct 07 '18 at 04:05 — user2473015, Oct 07 '18 at 04:05

Ray Toal · Answer 1 · 2018-10-06T16:08:46.543

To see if the property payment exists in the object payload you can write

'payment' in payload

or if you want to know if the property is directly defined in the object (as opposed to being inherited through the prototype), say

payload.hasOwnProperty('payment')

The expression payload.payment, when the value is 0, will produce false when used as a boolean. This is because the following values will always act like false:

0
false
NaN
undefined
null
empty strings

The technical term for these values, that act as false, is "falsy." So because 0 is falsy, whenever you write !payload.payment, this value is actually true for 0 and false for everything else. Check for the missing property using one of the two techniques above (in or hasOwnProperty).

I found `has` in `lodash` also do this. – user2473015 Oct 07 '18 at 04:04 — user2473015, Oct 07 '18 at 04:04

JS Check property exists for number values

1 Answers1