Playground link

class Person {
    firstName!: string; // required
    lastName!: string;  // required
    isAdult = true      // optional, has default

    // OPTION specify only required fields
    // constructor(params: Partial<Person> & Pick<Person, "firstName" | "lastName">) {
    // OPTION specify only optional fields
    // constructor(params: Omit<Person, "isAdult"> & Partial<Pick<Person, "isAdult">>) {
    // OPTION specify required and optional fields explicitly
    // constructor(params: Required<Pick<Person, "firstName" | "lastName">> & Partial<Pick<Person, "isAdult">>) {
    // OPTION using a cutom build type
    constructor(params: Dataclass<Person, "firstName" | "lastName">) {
        Object.assign(this, params)
    }

}
// we can also build custom types to simplify above constructors
type Dataclass<T, Required extends keyof T> = Partial<T> & Pick<T, Required>

let p = [
    // correct
    new Person({
        firstName: "Bob",
        lastName: "Dylan",
    }),
    new Person({
        firstName: "Bobby",
        lastName: "Dylan",
        isAdult: false,
    })
]

console.log(p)

// now we can use our favorite object syntax like spreading
let partialPerson = {
    firstName: "Bobby",
    isAdult: false,
}
let completePerson = new Person({
    lastName: "Dylan",
    ...partialPerson,
})

// following should always be wrong. required fields are not set
new Person({
    firstName: "Bob",
})

new Person({
})

new Person({
    firstName: "Bobby",
    lastName: undefined,
})