Nodejs: Classes - Syntactic sugar for function constructors and prototypal inheritance

classes.js

// classes.js

'use strict'

var Person = class Person {
    // function Person (args) {}
    constructor (firstname, gender) {
            this.firstname = firstname
            this.gender = gender
    }

    // function.prototype.introduce () {}
    introduce () {
        console.log(`${ this.designation[this.gender] }. ${ this.firstname } says hello! `)
    }

}

Person.prototype.designation = {
        m: 'Mr',
        f: 'Mdm'
    }

// utils.inherit(Singaporean, Person)
var Singaporean = class Singaporean extends Person {
    constructor( firstname, gender, favSinglishWord) {
        // Person.call(this)
        super(firstname, gender)
        this.favSinglishWord = favSinglishWord
    }

    // overwrite function
    introduce () {
        console.log(`${ this.designation[this.gender] }. ${ this.firstname } says hello ${ this.favSinglishWord }!`)
    }
}

module.exports = {
    Person : Person,
    Singaporean : Singaporean

}

index.js

var Person = require('./classes').Person
var Singaporean = require('./classes').Singaporean

var jane = new Person('jane','f')
var jon = new Person('john', 'm')
jane.introduce()
jon.introduce()

var tim = new Singaporean('tim','m','lah')
tim.introduce()