The JavaScript JSON Cookbook

How to declare interfaces using TypeScript

An interface defines how something behaves, without defining the implementation. In TypeScript, an interface names a complex type by describing the fields it has. This is known as structural subtyping.

How to do it…

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);

How it works…

The interface keyword in TypeScript defines an interface; as I already noted, an interface consists of the ...