How We Learned To Stop Worrying And Love JavaScript @danwrong @angustweets

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Rethinking twitter.com ‣ Use the right tool for the job. Don’t JavaScript all the things. ‣ Take advantage of the browser and of the nature of JavaScript rather than fighting it.

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Reuse patterns that make use of JavaScript rather than fight it

The hardest part...

The hardest part...

The hardest part...

So, talking animals it is... meow!!

Prototypes ‣ JavaScript’s Agent of Re-use ‣ Flexible but Awkward ‣ new syntax encourages classical model ‣ Prototype chains are single rooted ‣ Inheritance syntax is gnarly

var Animal = function(gender, says) { this.gender = gender; this.says = says; }; var WalkingAnimal = function(gender, says) { Animal.call(this, gender, says); } WalkingAnimal.prototype = new Animal(); // http://jsfiddle.net/96BSq/

var Animal = function(gender, says) { this.gender = gender; this.says = says; }; var WalkingAnimal = function(gender, says) { Animal.call(this, gender, says); } WalkingAnimal.prototype = new Animal(); // http://jsfiddle.net/96BSq/

Class syntax ‣ JS native class syntax scheduled for ES6 ‣ class, extend and super are reserved words ‣ Library implementation varies widely and abstraction is often leaky (‘const’, ‘static’) ‣ In particular, the relationship between this and super is difficult

//Prototype.js var SwimmingAnimal = Class.create(Animal, { type: 'SwimmingAnimal', speak: function($super) { return $super() + ", glug"; } }); //Dustin Diaz's "klass" var Alien = SuperHuman.extend({ beem: function() { this.supr(); // beem into space } });

//Prototype.js var SwimmingAnimal = Class.create(Animal, { type: 'SwimmingAnimal', speak: function($super) { return $super() + ", glug"; } }); //Dustin Diaz's "klass" var Alien = SuperHuman.extend({ beem: function() { this.supr(); // beem into space } });

//Prototype.js var SwimmingAnimal = Class.create(Animal, { type: 'SwimmingAnimal', speak: function($super) { return $super() + ", glug"; } }); //Dustin Diaz's "klass" var Alien = SuperHuman.extend({ beem: function() { this.supr(); // beem into space } });

Class hierarchies

Class hierarchies WTF? I walk too!

Class hierarchies Duck? WTF? I walk too!

Class hierarchies Duck? WTF? I walk too!

Classical inheritance ‣ Requires up-front knowledge of general case ‣ Single rooted hierarchy ‣ Types are often too generalized to map to real life coding problems (some animals swim AND walk)

Beyond classification ‣ 19th century British philosophers Whewell and Jevons argued that there are no objectively “right” classifications ‣ “In general, when working with prototypes, one typically chooses not to categorize but to exploit alikeness.” Antero Taivalsaari (Nokia Research Center) - Journal of Object Oriented Programming Nov/Dec 1997

Mixins ‣ JavaScript has first class functions ‣ Any property can be assigned to any object

//A property copy mixin var withWalking = { walk: function() { console.log('walking'); }, turn: function(direction) { console.log('turning', direction); }, stopWalking: function() { console.log('stopped walking'); } };

var extend = function(destination, source) { for (var k in source) { if (source.hasOwnProperty(k)) { destination[k] = source[k]; } } return destination; }; extend(Crocodile.prototype, withWalking); extend(Crocodile.prototype, withSwimming); //http://jsfiddle.net/29tW5/

Property copy mixins ‣ No hierarchical constraints ‣ Functionality is grouped by what it does not who it belongs to ‣ BUT... ‣ Mixin has no reference to target properties ‣ Properties can only clobber ‣ Target object requires intimate knowledge of mixin properties

Functional mixins ‣ Mixins are functions that assign properties to the ‘this’ object. ‣ Mixins are directly invoked in the context of the target object by means of call/apply

var withWalking = function() { this.walk = function() { console.log('walking'); }; this.turn = function(direction) { console.log('turning', direction); }; this.stopWalking = function() { console.log('stopped walking'); }; }; //http://jsfiddle.net/uyZZL/13/

function Crocodile(name, gender) { this.name = name; this.gender = gender; }; Crocodile.prototype.stalkTourists = function() { //.. }; withWalking.call(Crocodile.prototype); withSwimming.call(Crocodile.prototype);

Advice: before, after and around ‣ A mixin that adds, underscore.js style, before(), after() and around() to an object. ‣ Other mixins can use this to augment existing methods.

withAdvice.call(Crocodile.prototype); function withFlu() { this.before(“walk”, function() { console.log('sniff'); }) } var sickCrocodile = new Crocodile(); withFlu.call(sickCrocodile); sickCrocodile.walk(); //"sniff, pad, pad, pad, pad"

function withCharacterCounter() { this.updateCounter = function() { //... }; //add advice after core initialize method this.after('initialize', function() { this.$counter = this.select('counter'); this.on('uiTextUpdated', this.updateCounter); }); }

Functional mixins ‣ Mixins as verbs instead of nouns. ‣ Mixins are functions. We can take advantage of closure scope, arguments and context. ‣ A mixin can be applied to any object type: prototype, instance, whatever. ‣ Advice allows functional mixins to augment existing functions, not clobber them. ‣ Works with the language, simple to understand, no surprises. Debuggable.

Putting it to work...

function Storage() { this.initialize.call(this, arguments); } function baseStorage() { this.initialize = function(namespace) { this.namespace = namespace } this.encode = function(item) { return JSON.stringify(item) } this.decode = function(item) { return JSON.parse(item) } if (window.localStorage) { localStorageEngine.call(this); return; } if (document.documentElement.addBehavior) { userDataEngine.call(this); return; } memoryStorageEngine.call(this); } withAdvice.call(Storage.prototype); baseStorage.call(Storage.prototype);

function localStorageEngine() { this.getItem = function(key) { return this.decode(localStorage.getItem(this.namespace + key)); } this.setItem = function(key, val) { return localStorage.setItem(this.namespace + key, this.encode(val)); } }

function memoryStorageEngine() { var store = {}; this.after('initialize', function() { this.store = store[this.namespace] = store[this.namespace] || {}; }); this.getItem = function(key) { return this.decode(this.store[this.namespace + key]); } this.setItem = function(key, val) { return this.store[this.namespace + key] = this.encode(val); } }

function withEncryption() { this.after('initialize', function(namespace, secret) { this.secret = secret; }); this.around('decode', function(decode, val) { return decode(aes.dec(val, this.secret)); }) this.around('encode', function(encode, val) { return aes.enc(encode(val), this.secret); }); } var encryptedStorage = new Storage('secretStuff'); withEncryption.call(encryptedStorage);

Overview ‣ Functional mixins and advice/AOP are the shit ‣ Make use of JavaScript’s biggest strength - functions ‣ Extremely simple ‣ Endless flexibility ‣ Drop your class implementations and use this stuff now

Questions?

@jointheflock Visit the booth and chat to us twitter.com/jobs Happy hour tonight Beer.js!