a look at interface and type declarations

Creating and using interfaces

interface
interface IUser {
  name: string;
  id: number;
}
 
class UserAccount {
  name: string;
  id: number;
 
  constructor(name: string, id: number) {
    this.name = name;
    this.id = id;
  }
}
 
const user: IUser = new UserAccount("Murphy", 1);

• in class UserAccount, the name and id fields exist, so they satisfy the given interface.
• the types of the fields are also validated.

when you specify an argument or return type in a function, you can...

arguments, return type
 
const user: IUser = new UserAccount("Murphy", 1);
/**]
 * function to pick out people with names longer than 20 characters
 */]
const filterWithLongName = (user:IUser) => user.name.length > 20;

1.1. Define the interface

Typescript interface
interface ILoc {
    lat: number,
    lng: number
};

class Hotel {
    name:string;
    id: number;
    lat:number;
    lng:number

    constructor(id:number, name:string, lat:number, lng:number) {
        this.name = name
        this.id = id
        this.lat = lat;
        this.lng = lng;
    }
}

class Busstop {
    stationId:string;
    lat:number;
    lng:number;
    constructor(stationId:string, lat:number, lng:number) {
        this.stationId = stationId;
        this.lat = lat;
        this.lng = lng;
    }
}
const members:ILoc[] = [];

members.push(new Hotel(98344,"awesome hotel", 12.3344, -135.1124));
members.push(new Hotel(47590,"so so beautiful hotel", 126.02993, 23.9013));
members.push(new Busstop("of283jf-sakkk2-gkk2k2", 123.3316, 11.93883));

• different classes can be held in one array as long as the names and types of the fields specified in the interface exist.
• it is okay to have separate fields except lat, lng.

you can also add an object literal for the above interface.

Typescript interface
mbers.push(new Hotel(47590,"so so beautiful hotel", 126.02993, 23.9013));
members.push(new Busstop("of283jf-sakkk2-gkk2k2", 123.3316, 11.93883));
members.push({lat: 123.3316, lng: 11.93883});

• allow lat, lng fields to be object literals if defined