CODEWITHSUNDEEP
typescript
hejkerooo
hejkerooo

Reputation: 787

Why Typescript allows null/undefined in function

Why Typescript allows to pass null / undefined there?

// "strictNullChecks": false
function someFun(param: (foo: any) => any) {}
someFun(null); // no error - incorrect
someFun(undefined); // no error - incorrect

Upvotes: 0

Views: 55

Answers (1)

jperl
jperl

Reputation: 5132

Quoting from the docs

In strict null checking mode, the null and undefined values are not in the domain of every type and are only assignable to themselves and any (the one exception being that undefined is also assignable to void)

..T and T | undefined are considered synonymous in regular type checking mode (because undefined is considered a subtype of any T),

Upvotes: 2

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