Maptest.ts

class User {
    userId: number = 0
    userName: string = ""
}

const user1: User = {
    userId: 1,
    userName: "user1"
}

const user2: User = {
    userId: 2,
    userName: "user2"
}

const userMap = new Map<number, User>()

userMap.set(user1.userId, user1)
userMap.set(user2.userId, user2)

console.log(userMap)
console.log(userMap.has(1))
console.log(userMap.get(1))
console.log([...userMap.keys()])
console.log([...userMap.values()])
const userArray = [...userMap.values()]

const newUserMap = new Map<number, User>(
    userArray.map(user => [user.userId, user])
)

console.log(newUserMap)

const fakeUser1: User = {
    userId: 1,
    userName: "fake user1"
}
const userArray2 = [fakeUser1, user1, user2]

const newUserMap2 = new Map<number, User>(
    userArray2.map(user => [user.userId, user])
)

console.log(newUserMap2)

const sameUser2:User = {
    userId:2,
    userName:"user2"
}

console.log(new Set([user2,sameUser2]))