Typescript example: Constructor with optional args via interface.

Person.ts

// 1. Define an interface for the optional args to your constructor.

interface PersonArgs {
    nickname?: string;
    age?: number;
}

class Person {

    // 2. Add the args as the last parameter of the constructor, with a default value of {}.

    constructor(private _name: string, private _args: PersonArgs = {}) {
    }

    /** Gets the name. */
    get name(): string {
        return this._name;
    }

    /** Gets the age, or undefined if not known. */
    get age(): number | undefined {
        return this._args.age;
    }

    /** Gets the nickname, or a default one. */
    get nickname(): string {
        return this._args.nickname || "Hey you";
    }

    /** Demonstrates use of getters. */
    describe() {
        alert("Given name: " + this.name + "\n"
            + "Nickname: " + this.nickname + "\n"
            + "Age:" + (this.age || "Unknown"));
    }
}

// 3. Create instances with known optionals given as an object.

new Person("Robert", { nickname: "Bob", age: 2 }).describe();
new Person("Sharon", { age: 42 }).describe();
new Person("Elmo").describe();