Declaring an interface is a little like declaring a structure or class; you define the fields in the interface, each with its own type, like this:

interface Record {
  call: string;
  lat: number;
  lng: number;
}

Function printLocation(r: Record) {
  console.log(r.call + ': ' + r.lat + ', ' + r.lng);
}

var myObj = {call: 'kf6gpe-7', lat: 21.9749, lng: 159.3686};

printLocation(myObj);

The interface keyword in TypeScript defines an interface; as I already noted, an interface consists of the fields it declares with their types. In this listing, I defined a plain JavaScript object, myObj and then called the function printLocation, that I previously defined, which takes a Record. When calling printLocation with myObj, the TypeScript...