index.ts

//Declaring object with no types
let user = { 
  id: 10,
  name: 'Rahul',
  email: 'a@g.com'
}

console.log(user.name)
// Rahul

console.log(user.email)
// a@g.com

console.log(user.number)
// error TS2339: Property 'number' does not exist on type '{ id: number; name: string; email: string; }'

user.age = 20
// error TS2339: Property 'age' does not exist on type '{ id: number; name: string; email: string; }'