CODEWITHSUNDEEP
typescripttypesconditional-statementsnullable
Marc
Marc

Reputation: 702

Conditional types for nullable in Typescript

I want to check if a type is nullable or not, and if it has a conditional type on the value.

I tried implementing

type IsNullable<T> = T extends null ? true : false;

However, it does not seem to work

type test = IsNullable<number> // Returns false as it should
type test = IsNullable<number | null> // Returns false when it should be true

What's the proper way of checking if a type is nullable? I tried with T extends null | T and did not work either.

Upvotes: 4

Views: 2991

Answers (1)

phry
phry

Reputation: 44096

You can switch the left and right side of the extends, so

type IsNullable<T> = null extends T ? true : false;

should work for you.

Upvotes: 10

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