How to leverage TypeScript to enforce an array is containing all property keys of an obejct type (and nothing else)?

I have a type describing an object

How to leverage TypeScript to enforce an array is containing all properties of an obejct type (and nothing else)?

I have a type describing an object

How to leverage TypeScript to enforce an array is containing all properties of an obejct type (and nothing else)?

I have a type describing an object

Why does array?.length still warn that the array might be undefined?

Given this code: