JavaScript OOP in NodeJS how

Question

I am used to the classical OOP as in Java   What are the best practices to do OOP in JavaScript using NodeJS    Each Class is a file with module export   How to create Classes   this Class   function           constructor      var privateField          this publicField          var privateMethod   function          this publicMethod   function           vs   I am not even sure it is correct   this Class         privateField           privateMethod  function             return           publicField             publicMethod  function                vs   this Class   function       this Class prototype method   function            How would inheritance work   Are there specific modules for implementing OOP in NodeJS    I am finding a thousand different ways to create things that resemble OOP   but I have no clue what is the most used practical clean way   Bonus question  what is the suggested  OOP style  to use with MongooseJS   can a MongooseJS document be seen as a Class and a model used as an instance    EDIT  here is an example in JsFiddle please provide feedback     http   javascriptissexy com oop-in-javascript-what-you-need-to-know  function inheritPrototype childObject  parentObject        var copyOfParent   Object create parentObject prototype      copyOfParent constructor   childObject     childObject prototype   copyOfParent      example function Canvas  id        this id   id     this shapes        instead of array      console log  Canvas constructor called   id    Canvas prototype         constructor  Canvas       getId  function             return this id             getShape  function shapeId            return this shapes shapeId              getShapes  function             return this shapes             addShape  function  shape             this shapes shape getId      shape             removeShape  function  shapeId             var shape   this shapes shapeId          if  shape              delete this shapes shapeId          return shape          function Shape id        this id   id     this size     width  0  height  0       console log  Shape constructor called   id    Shape prototype         constructor  Shape       getId  function             return this id             getSize  function             return this size             setSize  function  size             this size   size            inheritance function Square id  otherSuff        Shape call this  id    same as Shape prototype constructor apply  this  arguments          this stuff   otherSuff     console log  Square constructor called   id    inheritPrototype Square  Shape  Square prototype getSize   function       override     return this size width    function ComplexShape id        Shape call this  id      this frame   null     console log  ComplexShape constructor called   id    inheritPrototype ComplexShape  Shape  ComplexShape prototype getFrame   function         return this frame   ComplexShape prototype setFrame   function frame        this frame   frame    function Frame id        this id   id     this length   0   Frame prototype         constructor  Frame       getId  function             return this id             getLength  function             return this length             setLength  function  length             this length   length               run var aCanvas   new Canvas  c1   var anotherCanvas   new Canvas  c2   console log  aCanvas     aCanvas getId     var aSquare   new Square  s1       aSquare setSize   width  100  height  100   console log  square overridden size    aSquare getSize     var aComplexShape   new ComplexShape  supercomplex   var aFrame   new Frame  f1   aComplexShape setFrame aFrame  console log aComplexShape getFrame     aCanvas addShape aSquare  aCanvas addShape aComplexShape  console log  Shapes in aCanvas    Object keys aCanvas getShapes    length   anotherCanvas addShape aCanvas removeShape  supercomplex    console log  Shapes in aCanvas    Object keys aCanvas getShapes    length  console log  Shapes in anotherCanvas    Object keys anotherCanvas getShapes    length   console log aSquare instanceof Shape  console log aComplexShape instanceof Shape

User · Answer

If you are working on your own  and you want the closest thing to OOP as you would find in Java or C  or C    see the javascript library  CrxOop  CrxOop provides syntax somewhat familiar to Java developers    Just be careful  Java s OOP is not the same as that found in Javascript  To get the same behavior as in Java  use CrxOop s classes  not CrxOop s structures  and make sure all your methods are virtual  An example of the syntax is   crx registerClass  ExampleClass            VERBOSE   1         public var publicVar   5        private var privateVar   7         public virtual function publicVirtualFunction   function x                  this publicVar1   x          console log  publicVirtualFunction                   private virtual function privatePureVirtualFunction   0         protected virtual final function protectedVirtualFinalFunction   function                   console log  protectedVirtualFinalFunction                 crx registerClass  ExampleSubClass           VERBOSE  1       EXTENDS   ExampleClass          public var publicVar   2         private virtual function privatePureVirtualFunction   function x                  this PARENT CONSTRUCT pA           console log  ExampleSubClass  privatePureVirtualFunction                  var gExampleSubClass   crx new  ExampleSubClass   4    console log gExampleSubClass publicVar   console log gExampleSubClass CAST  ExampleClass   publicVar     The code is pure javascript  no transpiling  The example is taken from a number of examples from the official documentation

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I suggest to use the inherits helper that comes with the standard util module  http   nodejs org api util html util util inherits constructor superconstructor  There is an example of how to use it on the linked page

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In the Javascript community  lots of people argue that OOP should not be used because the prototype model does not allow to do a strict and robust OOP natively  However  I don t think that OOP is a matter of langage but rather a matter of architecture   If you want to use a real strong OOP in Javascript Node  you can have a look at the full-stack open source framework Danf  It provides all needed features for a strong OOP code  classes  interfaces  inheritance  dependency-injection        It also allows you to use the same classes on both the server  node  and client  browser  sides  Moreover  you can code your own danf modules and share them with anybody thanks to Npm

User · Answer

This is the best video about Object-Oriented JavaScript on the internet   The Definitive Guide to Object-Oriented JavaScript  Watch from beginning to end    Basically  Javascript is a Prototype-based language which is quite different than the classes in Java  C    C   and other popular friends  The video explains the core concepts far better than any answer here   With ES6  released 2015  we got a  class  keyword which allows us to use Javascript  classes  like we would with Java  C    C   Swift  etc   Screenshot from the video showing how to write and instantiate a Javascript class subclass

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This is an example that works out of the box  If you want less  hacky   you should use inheritance library or such   Well in a file animal js you would write   var method   Animal prototype   function Animal age        this  age   age     method getAge   function         return this  age      module exports   Animal    To use it in other file   var Animal   require    animal js     var john   new Animal 3     If you want a  sub class  then inside mouse js   var  super   require    animal js   prototype      method   Mouse prototype   Object create   super     method constructor   Mouse   function Mouse          super constructor apply  this  arguments        Pointless override to show super calls   note that for performance  e g  inlining the below is impossible    you should do   method  getAge    super getAge    and then use this  getAge   instead of super   method getAge   function         return  super getAge call this       module exports   Mouse    Also you can consider  Method borrowing  instead of vertical inheritance  You don t need to inherit from a  class  to use its method on your class  For instance    var method   List prototype   function List           method add   Array prototype push          var a   new List     a add 3    console log a 0     3

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As Node js community ensure new features from the JavaScript ECMA-262 specification are brought to Node js developers in a timely manner   You can take a look at JavaScript classes  MDN link to JS classes  In the ECMAScript 6 JavaScript classes are introduced  this method provide easier way to model OOP concepts in Javascript   Note   JS classes will work in only strict mode   Below is some skeleton of class inheritance written in Node js   Used Node js Version v5 0 0    Class declarations     use strict    class Animal    constructor name       this name   name        print        console log  Name is     this name         var a1   new Animal  Dog      Inheritance     use strict   class Base    constructor           methods definitions go here    class Child extends Base      methods definitions go here  print           var childObj   new Child

[javascript] JavaScript OOP in NodeJS: how?

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