Typescript says that the index property of individual matchAll() matches is (number

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Typescript says that the index property of individual matchAll() matches is (number | undefined)

Time：01-14

I get an error

Type '(number | undefined)[]' is not assignable to type 'number[]'.

when I write

const nums: number[] = [...'a'.matchAll(/a/g)].map(match => match.index);

but MDN doesn't say anything about this property being optional. Is this a bug or am I missing something?

CodePudding user response：

It's a bug in TypeScript; the issue has been reported in 2020. For now, you can safely assert that match.index is a number.