Three different ways to use javascript functions, but I do not know the pros and cons. Can someone explain the differences?

Question

I have three ways to make a function and return it. (Maybe there is more?), But I do not know the differences between them and when to use. Can someone explain.

var test1 = function() { var funk1 = function() { console.log(1); } var funk2 = function(msg) { console.log(msg); } return { funk1: funk1, funk2: funk2 } }; var test2 = function() { this.funk1 = function() { console.log(1); } this.funk2 = function(msg) { console.log(msg); } }; var someThing = test1(); someThing.funk1(); someThing.funk2(2); var someThing = new test1(); someThing.funk1(); someThing.funk2(2); var thingElse = new test2(); thingElse.funk1(); thingElse.funk2(2); 

Answer 1

This is a module / library / plugin template

 var test1 = function() { var funk1 = function() { console.log(1); } return { funk1: funk1 } }; 

This is an OOP (Object-Oriented-Programming) pattern

 var test2 = function() { this.funk1 = function() { console.log(1); } }; 

Difference

 var t = test1() //function call, t is result of test1 function execution var t = new test1() //instance initialization, t is instance of test1 class 

Consider this simple model.

We have a manufacturer that makes cars, the manufacturer has some methods, and the car has its own methods, we will not configure the manufacturer’s public properties, but we still cannot access the technology that the manufacturer uses to create the car, so the car is a black box that exposes some public details and cannot be changed.

 //service for creating/controlling manufactorer var ManufacturerService = function(companyName) { var self = this; self.companyName = companyName; //encapsulation var Car = function(name, number){ var createdAt = new Date(); var engineStarts = 0; //instance property, doesn't have setter Object.defineProperty(this, 'info', { get: function(){ return { name: name, createdAt: createdAt, engineStarts: engineStarts } } }); //instance method this.startEngine = function(){ //private property, available only on instance, and cannot be extracted engineStarts++; //reference to ManufacturerService.companyName console.log(self.companyName + ' ' + name + ':' + number + ' engine Started'); } } var createCar = function(name){ //check cache/duplication/validation //or use custom behavior var carNumber = ManufacturerService.genShortUid(); return new Car(name, carNumber); } var getName = function(){ return self.companyName; } return { getName: getName, createCar: createCar } }; //static method, this can be overriden by 3rdParty or user ManufacturerService.genShortUid = function genShortUid() { return ('0000' + (Math.random()*Math.pow(36,4) << 0).toString(36)).slice(-4); } 

Using ManufacturerService is written as a plugin / library, but note that the car model is fully encapsulated, which means that the model is completely hidden from the outside world

 //create a service instance var VolvoCompany = new ManufacturerService('Volvo'); //access encapsulated Car model by createCar method //which is available only on instance of service var Golf = VolvoCompany.createCar('Golf'); //instance method of car Model Golf.startEngine(); //logs Volvo Golf:vnv6 engine Started Golf.info //returns Object {name: "Golf", createdAt: Sat Feb 13 2016 17:39:57 GMT+0600 (ALMT), engineStarts: 1} //try to hack car instance Golf.info.name = 'test'; Golf.name = 'test'; Golf.info //returns same object, as Car model doesn't have exported setters Object {name: "Golf", createdAt: Sat Feb 13 2016 17:39:57 GMT+0600 (ALMT), engineStarts: 1} //customize guid generator of ManufacturerService ManufacturerService.genShortUid = function(){ return '1111'; } //reuse same service for another Car model var Mazda = VolvoCompany.createCar('Mazda'); //instance method of car Model Mazda.startEngine(); //logs Volvo Mazda:1111 engine Started 

Summary

ManufacturerService exports a limited number of methods and opens completely, but the Car instance is fully encapsulated and not even visible

corrections / suggestions / comments are welcome