Type 'undefined' is not assignable to type 'string' when destructing an object

Issue

I'm destructing an object as following:

const { lang, ...params } = ctx.query;

But TS gives me an error in this line:

if (!value.includes(params[key])) return false;

How can I solve this issue?

Solution

Use .includes(params[key] as string) (or .includes(<string>params[key])) to tell Typescript you know it's a string.

Answered By - Jeremy Thille