containing the "You have a really long name!" driveBackward: function () { The pattern was originally designed by Trygve Reenskaug during his time working on Smalltalk-80 (1979) where it was initially called Model-View-Controller-Editor. }. var collection = $( "#elem" ).data( "myobj" ); this.observers = new ObserverList(); price: 0.3 this.doors = doors || 4; //********************** Snippet 1 **********************// getModel() { // Augment the Car constructor to include "driveForward" and "driveBackward" }; For this, we're first going to go through my variation of the Coffee example from an excellent book called Head First Design Patterns by Freeman, Sierra, and Bates, which is modeled around a Macbook purchase. // var store = window.store || {}; for ES5 and earlier versions Developers would rely on separate scripts to split and organize reusable chunks of logic and it wasn't a surprise to find 10-20 scripts being imported manually in an HTML file just to keep things tidy. // 2. Developers would rely on separate scripts to split and organize reusable chunks of logic and it wasn't a surprise to find 10-20 scripts being imported manually in an HTML file just to keep things tidy. Although the term CommonJS AMD format has been seen in the wild on occasion, it's best to refer to it as just AMD or Async Module support as not all participants on the CommonJS list wished to pursue it. RequireJS And The jQuery UI Widget FactoryAs we covered in the section on Modern Module Design Patterns, RequireJS is an AMD-compatible script loader that provides a clean solution for encapsulating application logic inside manageable modules.Its able to load modules in the correct order (through its order plugin), simplifies the process of combining scripts via its excellent r.js optimizer and provides the means for defining dynamic dependencies on a per-module basis.In the boilerplate pattern below, we demonstrate how an AMD (and thus RequireJS) compatible jQuery UI widget can be defined that does the following:Allows the definition of widget module dependencies, building on top of the previous jQuery UI Widget Factory pattern presented earlier.Demonstrates one approach to passing in HTML template assets for creating templated widgets (using Underscore.js micro-templating).Includes a quick tip on adjustments that we can make to our widget module if we wish to later pass it through to the RequireJS optimizer. If when using Knockouts MVVM we find yourself dissatisfied with the idea of application logic being overly tied into your View, we can change this. var shorterAccess1 = myNS.hello.world; // Handle it asynchronously to allow scripts the opportunity to delay ready truck.setModel( "CAT" ); console.log('The model of this vehicle is..' + this.model); // A new instance of Superhero can be created as follows. } // function privateMethod() { // that the following files are all in the same directory: } // set up event handlers for those objects. var singletonTest = SingletonTester.getInstance({ What's the most efficient way to query for this collection of elements? // no longer listening define(["jquery"], function ( $ ) { saySomething() { e.preventDefault(); // arrange a viewing // vehicle: car, model:default, license: 00000-000 $.get( url, data, callback, dataType ); toolbars: { Imagine that we have a script where for each DOM element found on a page with class "foo" we wish to increment a counter. }; events: { Flyweight for Performance OptimizationUsing DOM element itself in jQuery: this.cost = 997; JavaScript doesn't really have built-in support for namespaces as other languages do, but it does have objects that can be used to achieve a similar effect. const flavor = newFlavor; summary: "Microsoft made $20 million", let myPrivateMethod; myCar.driveBackward(); // Outputs: $.fn.plugin = function( options ) { // A constructor for defining new cars When given a DOM node, does it contain any data-bindings? //*******************************************************// price: 0.3, // or Working with a local variable here is almost always faster than working with a top-level global (e.g.myApp). // Extend the controlling checkbox with the Subject class } }, AdvantagesThis pattern allows the syntax of our scripts to be more consistent. In this section well review three of these categories and briefly mention a few examples of the patterns that fall into these categories before exploring specific ones in more detail. # The Facade PatternNotes on abstractionFacades are a structural pattern that can often be seen in JavaScript libraries like jQuery where, although an implementation may support methods with a wide range of behaviors, only a "facade" or limited abstraction of these methods is presented to the public for use.Did you know however that getElementById() on its own is significantly faster by a high order of magnitude? // Outputs: 5 this.prototype = parentClassOrObject; var style = elem.style, var creator = function( val ) { It makes decisions on when to call which objects, based on the actions (or inaction) of other objects and input. At minimum it normalizes the cross-browser differences between XHR (XMLHttpRequest) and makes it trivial for us to perform common HTTP actions (e.g get, post etc), work with Deferreds and so on. function Car( model, year, miles ) { return 900.00; // from receiving any new topic notifications as follows: "add4GBRam", return `You have successfully purchased Item ${id}, a ${model}`; In this scenario, a target object can be decorated with new functionality without necessarily breaking or overriding existing methods in the source/superclass object (although this can be done). A simpler example of how to use observables arrays may look as follows: // perform a similar existence check when defining nested testModule.resetCounter(); Here good and bad are considered in context - a perfect design may qualify as an anti-pattern if applied in the wrong context. Some of these developers (such as Alex Russell) had been keeping a close eye on the evolution of JavaScript usage for large-scale development and were acutely aware of the need for better language features for writing more modular JS. } // bridge allows us to call public methods // window and document are passed through as local The way some developers are approaching choosing which format to use is opting for CommonJS when a module can be used in a server-side environment and using AMD if this is not the case.As AMD modules are capable of using plugins and can define more granular things like constructors and functions this makes sense. var mediator = {}; truck.setModel = function( modelName ){ } } * Licensed under the MIT license this.ISBN = ISBN; }, // Define a vehicle factory function init() { A trimmed down KnockoutJS View for this, including all the necessary data-bindings may look as follows. // Create a new instance of our Todo constructor The GoF do not refer to MVC as a design pattern, but rather consider it a set of classes to build a user interface. test.bar(); var carManager = { "enabled" : "disabled") ); updateMyConfig: function( newConfig ) { defaults: { functionKey: function () { YUISimilarly, we can also implement the Module pattern when building applications using YUI3. // Outputs: true Bugs Fixed: Annotation: Hatch: Annotation: Return _StartPoint and _EndPoint to the gradient hatch edit stop command line options (RH-61328) Annotation: Leader: Blank leader shows Many developers enjoyed using AMD and one could consider it was a reliable stepping stone towards JavaScript Modules which were not available at the time. $.ajax({ All workflow and business logic that needs to be kicked off is put directly into the object that triggers the events and the objects that handle the events. decoratorApp = { 'basket.core', The following snippets of code provide the implementation of the Singleton pattern using JavaScript functions. Here's the interface we're going to define for the Macbook: To make it easier for us to add as many more options as needed, later on, an Abstract Decorator class is defined with default methods required to implement the Macbook interface, which the rest of the options will sub-class. this.topics[topic].push({ console.log('jumping'); // Outputs: Truck object of color "red", a "like new" state Real-time stock-price grid update using publishers and subscribers implemented in classic JavaScript. // [uiObject] ) // this example, which we first cache pubsub.publish( "inbox/newMessage", { // Storage for our vehicle types ;(function ( $, window, document, undefined ) { console.log(todoItem.methods.placeOrder()); // Outputs: } var MenuItem = MyFrameworkView.extend({ if (el.addEventListener) { // Define the prototypes and utilities for this factory Text Shadow. clickedIt: function(e){ // Subscribers var _private = { // this.options.someValue = doSomethingWith( value ); return `${this.model} has done ${this.miles} miles`; getModel: function () { How this is implemented can vary, but one approach is to have the manager object contain a central database of the extrinsic states and the flyweight objects to which they belong. enumerable: true In MVP, all of this complex logic can be encapsulated in a presenter, which can simplify maintenance greatly.As MVP views are defined through an interface and the interface is technically the only point of contact between the system and the view (other than a presenter), this pattern also allows developers to write presentation logic without needing to wait for designers to produce layouts and graphics for the application.Depending on the implementation, MVP may be easier to automatically unit test than MVC. // ES2015+ keywords/syntax used: const, let, arrow function syntax Post-initialization, the logic for changing options It acts as a base class from which others are derived. This can also be expanded using the object literal pattern to be: One of the obvious challenges with this pattern is that each additional layer we wish to create requires yet another object to be defined as a child of some parent in our top-level namespace. arr.push(next); function memory( macbook ) { console.log( movingTruck ); var truckFactory = new TruckFactory(); $("a").map(function() { As MVP views are defined through an interface and the interface is technically the only point of contact between the system and the view (other than a presenter), this pattern also allows developers to write presentation logic without needing to wait for designers to produce layouts and graphics for the application. // We can also unsubscribe if we no longer wish for our subscribers Although the idea of (yet) another module format may be daunting, we will cover UMD briefly for the sake of thoroughness.We originally began defining UMD by taking a look at the simplified CommonJS wrapper supported in the AMD specification. Radio.js (http://radio.uxder.com/), PubSubJS (https://github.com/mroderick/PubSubJS) or Pure JS PubSub by Peter Higgins (https://github.com/phiggins42/bloody-jquery-plugins/blob/55e41df9bf08f42378bb08b93efcb28555b61aeb/pubsub.js) are also similar alternatives worth checking out. Extending Singletons }); var privateVar = "Ben Cherry", addNewEmployee: function(){ Using objects, the module pattern was just one way to encapsulate logic in a file with both public and "private" methods. update() { A lightweight wrapper around the constructor, which helps to avoid issues such as multiple instantiations. Here's one that covers namespacing, public and private variables: A developer working on such a system who hasnt worked on the application before may introduce a bad design into the project by accident. takeOrders('Frappe', 1); var types = {}; ); wheelSize: "medium", How are you doing today?" console.log( myBigTruck ); "anotherKey": { A footnote in Microsoft's submission to the UK's Competition and Markets Authority (CMA) has let slip the reason behind Call of Duty's absence from the Xbox Game Pass library: Sony and Both classic JavaScript, as well as ES2015+ do not support interfaces. return node.getAttribute ? In modern frameworks, the observer pattern is used to notify components of changes in state. it's still a considerable quantity of objects, but significantly fewer than we had previously.An instance of the following book meta-data combination will be created for all required copies of the book object with a particular title/ISBN. JavaScript however, has been around for many decades now and has gone through multiple revisions. At this point we have our gradient in the background, and the text is displayed on top of it. Here is one example with the pattern being used in this context: The disadvantages of the Module pattern are that as we access both public and private members differently, when we wish to change visibility, we actually have to make changes to each place the member was used. // Outputs: 900.00 module.doStuff(); MacbookWith8GBRamAndEngraving = function(){}, getFlavor() {}, console.log(`Name:${privateVar}`); One of the downsides to this however is that a level of interpretation is needed between the ViewModel and the View and this can have performance costs. Can also be applied more than once to different selectors, for having more than one style of divider in the same project, using SCSS. var Superhero = function( firstName, lastName, powers ){. stockPrice: 570.91 // 1. extend namespace with a "utils" object Node treats files ending in `.mjs` and ending in `.js` with a top-level `type` field value of `module` as JavaScript Modules. const basket = new WeakMap(); run: function() { The disadvantages of this pattern are that there may be easier or more optimal approaches to achieving this goal (e.g. The abstract factory can be named abstractVehicleFactory. The challenge with this particular Facade is that to provide an elegant selector function capable of accepting and parsing multiple types of queries, there is an implicit cost of abstraction. If the prototype of the constructor function used contains a property called name for example (as per the code sample lower down), then each object created by that same constructor will also have this same property.Reviewing the definitions for this pattern in existing (non-JavaScript) literature, we may find references to classes once again. // ECMAScript 3 compatible approaches The reality however is that MVVM does this for a number of good reasons (which weve covered), including facilitating designers to more easily bind to logic from their markup. // via this.options this.element.addStuff(); module.errorColor = "red"; } console.log(secondInstance); controlCheckbox.notify( controlCheckbox.checked ); // Establish a safe, transparent sharing space. takeOrders('Cappuccino', 97); instance = this; } ConclusionsThat's it for this introductory adventure into the world of design patterns in JavaScript and jQuery - I hope you've found it beneficial.Design patterns make it easy for us to build on the shoulders of developers who have defined solutions to challenging problems and architectures over a number of decades. console.log(todoItem.methods.summary()); // map array of passed in todos to an observableArray of Todo objects A Facade is then used to supply a much simpler API to accessing these methods: break; value: 'Ford', so bad" init() { This is significantly more easy to use for selecting HTML elements on a page versus having to manually opt for getElementById(), getElementsByClassName(), getElementsByTagName() and so on. It is also of great help to comment your plugin code. Whilst this book is targeted at both beginners and intermediate developers, a basic understanding of JavaScript fundamentals is assumed. Facade with Module The classic JavaScript design patterns book, updated to ES2015+ syntax. This is where the objects in a system may subscribe to other objects and be notified by them when an event of interest occurs. } # The Mediator PatternThe Mediator Pattern is a design pattern that allows one object to notify a set of other objects when an event occurs. We would all be forgiven for thinking there is nothing wrong with this - technically, it's completely valid JavaScript. // if there there is no filter style applied in a css rule, we are done // return basket If the input exceeds 10 characters, it will display, otherwise it will remain hidden.Moving on to a more advanced example, we can return to our Todo application. // Our plugin "core" is exposed under a core namespace in Dynamic import can also be supported using the await keyword: With dynamic import, the module graph is only downloaded and evaluated when the module is actually used. // We used the destructuring assignment syntax that makes it possible to unpack values from data structures into distinct variables. Converting code to use the Flyweight patternNext, let's continue our look at Flyweights by implementing a system to manage all of the books in a library. The observer nature of this relationship is also what facilitates multiple views being attached to the same model. // ES2015+ keywords/syntax used: const, class, extends, console.log( myApp.utils.getValue() ); console.log( "Caching is: " + ( this.myConfig.useCaching ? Clone() {} About Our Coalition. toggleViewed: function() { Both classic JavaScript, as well as ES2015+ do not support interfaces. // decides what should happen next module.facade({ augment( Car, Mixin, "driveForward", "driveBackward" ); class VehicleFactory { jQuerys on method as an event aggregator is a great example of too many objects to listen to. start: publicFunction, The VehicleFactory can create a new vehicle object, car, or truck based on the vehicleType passed.There are two possible approaches to building trucks using the VehicleFactory classApproach #1: Modify a VehicleFactory instance to use the Truck class subscribers[len].func(topic, args); if( instance === undefined ) { console.log( "drive forward" ); One may find the Underscore.js extend() method a simpler, more cross-browser implementation to start with http://documentcloud.github.io/underscore/docs/underscore.html#section-82. Let us look at an implementation of the module pattern that uses the WeakMap object.Basic module Definition clickedIt(e) { In the Strategy pattern regard, the view delegates to the controller at the view's discretion. console.log( "Data output:" + data ); }, takeOrders('Xpresso', 3); }) { var badSingleB = myBadSingleton.getInstance(); }); Although these behaviors can be mapped to properties, the View is still responsible for handling events from the ViewModel.Its important to remember the View isnt responsible here for handling state - it keeps this in sync with the ViewModel.A KnockoutJS View is simply a HTML document with declarative bindings to link it to the ViewModel. var badSingleB = myBadSingleton.getInstance(); const properties = {