Index signatures

interface StringArray {
  [index: number]: string;
}
 
const myArray: StringArray = getStringArray();
const secondItem = myArray[1];

interface NumberOrStringDictionary {
  [index: string]: number | string;
  length: number; // ok, length is a number
  name: string; // ok, name is a string
}

interface ReadonlyStringArray {
  readonly [index: number]: string;
}