typescript_equality.ts

type CustomerId = number
type OrderId = number

let customerId: CustomerId
let orderId: OrderId

customerId = 42
orderId = 42

if (customerId == orderId) {
  console.log('Typescript says they are equal')
}

// 2nd attempt:

enum CustomerIdBrand {}
type CustomerId2 = CustomerIdBrand & number

enum OrderIdBrand {}
type OrderId2 = OrderIdBrand & number

let customerId2: CustomerId2
let orderId2: OrderId2

customerId2 = 42
orderId2 = 42

if (customerId2 == orderId2) {
  console.log('Typescript says they are equal?!')
}

// 3rd attempt:

interface CustomerId3 {
  _customerIdBrand: void
  value: number
}

interface OrderId3 {
  _orderIdBrand: void
  value: number
}

let customerId3: CustomerId3 = { value: 42 } as CustomerId3
let orderId3: OrderId3 = { value: 42 } as OrderId3

// error TS2365: Operator '==' cannot be applied to types 'CustomerId3' and 'OrderId3'
// if (customerId3 == orderId3) { console.log('Finally!') }

let {value} = customerId3
console.log(value)

let {value: innerValue} = customerId3
console.log(innerValue)