2022-04-23 13:26:53 +01:00
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---
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2022-09-06 15:44:40 +01:00
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categories:
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- Programming Languages
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2022-04-23 13:26:53 +01:00
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tags:
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- typescript
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---
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2022-07-04 14:45:26 +01:00
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# Unknown
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2024-02-02 15:58:13 +00:00
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You might think that a good use case for `any` is a scenario where you don't
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know in advance what the data type is going to be.
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2022-07-04 14:45:26 +01:00
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2024-02-02 15:58:13 +00:00
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In order to mark that this is the case, you type the value as `any`. In fact,
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TypeScript provides a type for this specific scenario: `unknown`.
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2022-07-04 14:45:26 +01:00
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2024-02-02 15:58:13 +00:00
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Like `any`, `unknown` is equivalent to every type in TS (it is also a supertype)
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but it is deliberately inhibiting, in contrast to `any`. When you use `unknown`
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you have to use type narrowing to avoid it being returned. So if your code
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starts with `unknown`, you should filter out scenarios where it evaluates to
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each of the possible types otherwise if `unknown` is returned it will cause an
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error.
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