Dynamic types in typescript

Question

How would one define the return type of the fn function below?

const fn = (propName1: string, propName2: string) => {
  return { 
   [propName1]: () => true 
   [propName2]: () => 'abc'
  }
}
const x = fn('customProp1', 'customProp2')
console.log(x.customProp1)
console.log(x.customProp2)

e.g.

type FN = (propName: string)=> {
  [propName1]: ()=>true
  [propName2]: ()=>string
}

This is for two custom methods, but ideally the solution should allow for any number of custom methods and properties.

Answer 1

As long as propName is a string, you can do:

type FN_return = {[propName: string]: ()=>true};