CODEWITHSUNDEEP
typescriptreduxoptional-chaining
ddominoo
ddominoo

Reputation: 11

Optional chaining property with 0 value

I have such code:

if (action?.notificationKey && state.notifications[action.notificationKey]) {
    delete state.notifications[action.notificationKey];
}

which does not satisfy me, because action.notificationKey can have 0 value and optional chaining condition is not fulfilled.

refactoring to:

    if ("notificationKey" in action && state.notifications[action.notificationKey]) {
      delete state.notifications[action.notificationKey];
    }

does not satisfy TS, and it underlines second condition as "TS2538: Type 'undefined' cannot be used as an index type"

how else I can check property with possible zero value existence?

edit: modified my question as I pasted previous code version, added optional chaining as it is currently

Upvotes: 0

Views: 255

Answers (1)

Carmine Tambascia
Carmine Tambascia

Reputation: 1928

The ?? (Nullish Coalescing) that can be used to set a default value if undefined or null should satisfied your requirements and both typescript with the first version a bit modified

I think it was introduced exactly for this cases. Please not that in order to work indeed you can get rid of the &&

if ((action?.notificationKey) ?? state.notifications[action.notificationKey]) {
  delete state.notifications[action.notificationKey];
}

Nullish coalescing operator (??)

So the if will be evaluated always( also when the value of nofiticationkey is 0) except when the first is null or undefined

Upvotes: 0

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