Typing Index Key

Without explicit declaration of key as index, the key passed to an object via object[key] will result in type error

const allTypes = {
  "thisthing": "",
  "anotherthing": "",
  "something": "find this",
};

const lookUpKey = "something";

// must delcare as keys of a type
const valueToLookFor = allTypes[lookUpKey as keyof typeof allTypes]

Combining Static and Dynamic Object Keys

interface MixedDictionary {
  // static
  staticKey: string;
  // dynamic = dictionary
  [key: string]: string | number;
}

const obj: MixedDictionary = {
  staticKey: "staticValue",
  dynamicKey1: "value-1",
  dynamicKey2: "value-2",
  dynamicKeyn: "value-n",
};