interface Runner {
  run: Function
}
interface Swimmer {
  swim: Function
}
type RunnerAndSwimmer = Runner & Swimmer; // Could be Runner & Swimmer & Dancer ....
const person: RunnerAndSwimmer = {
  run: function() {
    console.log('I can run!')
  },
  swim: function () {
    console.log('I can swim!')
  }
};
person.run(); // prints I can run
person.swim(); // prints I can swim