Is there a way to check for keys in a TypeScript object that I am not familiar with?

I have a good understanding of the unknown type in TypeScript. I am dealing with untrusted input that is typed as unknown, and my goal is to verify if it contains a truthy value under the key input.things.0.

function checkGreatness(input: unknown) {
  return Boolean(input?.things?.[0]);
}

Although I acknowledge that the type is 'unknown', TypeScript throws an error stating Object is of type 'unknown'. Despite this, my intention is to validate the value associated with that specific key.

Is there a way to perform key checks on an unknown object in TypeScript?

typescript

Answer №1

When it comes to ensuring safety and incorporating runtime code for type-checking, the level of caution you exercise is crucial.

If your primary concern is simply obtaining a boolean outcome, one approach is to cast the 'input' as 'any' and handle it with a try...catch block that yields false in the catch segment:

function isFullOfGreatThings (input: unknown): boolean { try { return Boolean((input as any)?.things?.[0]); } catch { return false; } }

To view the compiled JS code from the TS Playground, refer to the link provided above.

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