#Inconsistent typings for arrays with nullish values

1 messages · Page 1 of 1 (latest)

scarlet summit
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I just found out that this code:

const arr = [1, 2, 3, null]; // number[] or (number | null)[] ?
const arr = [1, 2, 3, undefined]; // number[] or (number | undefined)[] ?

gives different typings results in different projects, and i'm not sure why this would change.

However this seems okay:

const arr = [1, 2, 3, '4']; // (number | string)[]

In Stackblitz, number[]: https://stackblitz.com/edit/typescript-mxv8v6?file=index.ts
In TS Playground, (number | null)[]: https://www.typescriptlang.org/play?#code/MYewdgzgLgBAhgJwQOQK4Bt0wLwwNoCMANDAEwkDMJYG6AugNwBQoksiCAqmACYCmAMwCWYPjxz5iZSiVS9BIsYxbho8JAGUoCEQHMJhEuRhUYAcgAsZ5UA

This difference is also present in some of my projects, and i don't know what config would influence this.

Does anyone know ?

obtuse lilyBOT
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@scarlet summit Here's a shortened URL of your playground link! You can remove the full link from your message.

Ourson#7202
Playground Link

Preview:ts const arrNull = [1, 2, 3, null] const arrUndefined = [1, 2, 3, undefined] const arrString = [1, 2, 3, "4"]

You can choose specific lines to embed by selecting them before copying the link.
soft raptor
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some may have exactOptionalPropertyTypes disabled

scarlet summit
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Inconsistent typings for arrays with nullish values

soft raptor
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since disabled is the default state

scarlet summit
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hmm exactOptionalPropertyTypes does change this behaviour.
However, i just found out strictNullChecks does, which seems obvious, now that i see it

#

!resolved

soft raptor
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ah woops, of course