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Object

Object Type​

//we can define the type of an object before using it
type Person={
  first:string,
  last:string,
  age:number
}
const printName=(person:Person)=>{
  console.log("Hi!"+person.first);
}

Nested object​

type Person={
  first:string,
  last:string,
  age:number,
  address:{
    street:string,
    city:string,
    postal:string
  }
}
const printCity = (person:Person)=>{
  console.log("You live in "+person.address.city);
}

Optional Property​

//where one or more properties can be optional
type Point={
  x:number,
  y:number,
  z?:number
}
const myLocation : Point = {x:5,y:1};

const = calculate(point:Point)=>{
  return point.x*point.y;
}

Readonly Modifier​

//cannot be changed once it is set
type User={
  readonly id:string,
  username:string
}

const user:User ={id:111,username:'tom'}
user.id = 222; //-----this will not work

Intersection Type​

type Person={name:string}
type Pet={breed:string}

type PersonwithPet = Person & Pet;

const a :PersonwithPet = {name:"john", pet:"collie"}