How to create interface based on properties of the object?

Question

I am using latest TypeScript and Angular and i have an object:

const obj: ObjInterface = {
 prop1: 1,
 prop2: 2,
 prop3: '3'
}

Also i have interface based on that object:

interface ObjInterface {
  prop1: number;
  prop2: number;
  prop3: string;
}

Is it possible to create interface of the array that consist only from properties of the obj?

const array: SomeInterface = ['prop1', 'prop2', 'prop3']; // OK
const array: SomeInterface = ['prop1', 'prop2', 'prop4']; // error

Answer 1

You can create an array of keys of a type using the keyof operator

interface ObjInterface {
    prop1: number;
    prop2: number;
    prop3: string;
}
const array: Array<keyof ObjInterface> = ['prop1', 'prop2', 'prop3']; // OK
const array2: Array<keyof ObjInterface> = ['prop1', 'prop2', 'prop4']; // error

Note This will be a compile time error, at runtime you can have different strings in the array if you venture outside the type system or if you use type assertions.