ES5 Classes vs. ES6 Classes (vs. Java Classes vs. Scala Classes)

classes.js

/* ES5-style class declaration */

function ParsedTime(hour, minute, second) {
  this.hour = hour
  this.minute = minute
  this.second = second
  this.toString = function () {
    return JSON.stringify(this)
  }
}
ParsedTime.fromDate = function (date) {
  return new ParsedTime(date.getHours(), date.getMinutes(), date.getSeconds())
}

/* ES6-style class declaration */

class ParsedTime {
  constructor(hour, minute, second) {
    this.hour = hour
    this.minute = minute
    this.second = second
  }
  toString() {
    return JSON.stringify(this)
  }
  static fromDate(date) {
    return new ParsedTime(date.getHours(), date.getMinutes(), date.getSeconds())
  }
}

/* Java class declaration */

class ParsedTime {
  int hour;
  int minute;
  int second;
  
  public ParsedTime(int hour, int minute, int second) {
    this.hour = hour;
    this.minute = minute;
    this.second = second;
  }
  
  public String toString() {
    return JSON.stringify(this);
  }
  
  public static ParsedTime fromDate(Date date) {
    return new ParsedTime(date.getHours(), date.getMinutes(), date.getSeconds());
  }
}

/* Scala class declaration */

class ParsedTime(hour: Int, minute: Int, second: Int) {
  def toString() = JSON.stringify(this)
}
object ParsedTime {
  def fromDate(date: Date) = new ParsedTime(date.getHours(), date.getMinutes(), date.getSeconds())
}

/* Haskell something-or-other */

data ParsedTime = ParsedTime { hour :: Int, minute :: Int, second :: Int } deriving Show

parsedTimeFromDate :: Date -> ParsedTime
parsedTimeFromDate date = ParsedTime (getHours date) (getMinutes date) (getSeconds date)