Enterprise js pratices

Enterprise JS PracticesREFERENCE ARCHITECTURE

Marjan Nikolovski

A professional senior software engineer and conference speaker who is mainly hooked on the .NET platform as development platform and its derivatives, but from time to time knows to kill some time with open source software.

Usually spends his time writing systems backend and testing cutting edge technologies.

In spare time actively participating in holding technical presentations on conferences and researching. Specially interested in Distributed programming, Software architecture, Middleware, SOA, Non-relational databases and Workflow driven systems.

Agenda

Word-Two;

JavaScript mistakes from the C# programmer

Solution structure;

Solution architecture;

Dependency management;

Product modules;

UI Components;

Event Driven Messaging;

Application routing;

Localization;

Logging

Word-Two

Enterprise JavaScript app - heavy data app that is hard to be maintained;

Development time increase as the complexity and the codebase grows up;

Frontend development usually not taken seriously;

Frontend development always underestimated and without certain development plan and architecture;

JavaScript mistakes from the C# programmer

Writing jQuery still requires knowledge of JavaScript;

Using global variables and functions;

Object literal;

Self-Executing Anonymous Function;

Revealing Module Pattern;

Array and object declaration gone bad;

False value understanding;

Default value testing;

Using wrong comparison operators;

Misusing For..in statement on Arrays;

Misusing For..in statement on Objects;

Function and Object Scope in JavaScript;

Not aware of JSLint;

Using global variables and functions

var invalid_username = "Username exists";

function log_in() {

//Placed in global scope when executed

invalid_username = "Really Bad";

}

//Bad way to prevent namespace clashing

function namespace_log_out() {

}

//Functions

window.log_in();

window.namespace_log_out();

//Global variables are available off window object

console.log(window.invalid_username);

console.log(window.log_in);

console.log(window.namespace_log_out);

Object literal

Similar to JSON syntax;

Provide properties and function by choise;

Everything defined in the object literal is public;

Pros Cons

Remove global namespaces to properties, variables and methods

Difficult to maintain and understand

Functionality can be added at a later point

No way to have private properties and/or methods

All properties and methods are public

//Object Literal declaring properties and methodsvar user_model = { //public property username: "Some user", //public method login: function() {}};

Self-Executing Anonymous Function

Non name function that executes after it is defined;

Isolate variables and functions from global namespace;

//Self-Executing Anonymous Function:(function() { //private variable var username = "Some username"; //private function function login() {} login();}());

Pros Cons

Hide implementation from external code

All information is hidden

The code runs only once

Complicated on first sight

Not using object literal notation

Revealing Module Pattern

Uses the concept of the Self-Executing Anonymous Function;

Store the result into a variable;

//Revealing Module Pattern (Public & Private)var user_proxy = (function() { var me = {}, //Private property

username = "Some username"; //Public property me.message = "A message"; //Public method me.Login = function() { pvtLogin(); }; //Private method function pvtLogin() { //Do something... } //Return just the public parts return me;}());

Pros Cons

Allow private and public properties and methods

Easy to understand

Array and object declaration gone bad

Many ways to create an object, but only one is the correct one;

Hesitate the temptation to use the new keyword;

// bad practicevar user = new Object();

// good practicevar user = {};

// bad practicefunction User(uname){ this.username = uname;}

var user = new User(‘test’);User.username == ‘test’

var user = User(‘test’);user.username != ‘test’user.username == window. username

False value understanding

Same goes for arrays. Many ways to create an array, but only one is the correct one;

// bad practicevar userList = new Array(10);userList[0] === undefined;userList.length == 10;

// good practicevar userList = [];

Default value testing

C#

If(user != null && user.Length > 0){ // do something}

JavaScript

If(user){ // do something}

OR

user = user || ‘default value’;

Using wrong comparison operators

JavaScript ninja behavior can sometimes gives us unexpected results;

Sometime value comparison is not what it looks like;

Always use === or !== when doing comparison in JavaScript;

// Unexpected comparisons0 == '‘ //true0 == ‘0’ //truefalse == '0‘ //truenull == undefined //true' \t\r\n ' == 0 //true

0 === '' //false0 === '0' //falsefalse === '0' //falsenull === undefined //false' \t\r\n ' === 0 //false

Misusing For..in statement on Arrays

Does not guarantee the order of the items that are going to be retrieved by the iterator;

The iterator can iterate both array and objects;

Bad declaration can result in incorrect iterator execution;

var user = { username: ‘Test’, name:’Some name’};

for(var data in user){ alert(data);}// outputs username, name

var userArray = [];userArray.push(‘data’)userArray.name = ‘Test’;

for(var data in user){ alert(data); alert(user[data]);}// outputs 0, name// outputs data, Test

Misusing For..in statement on Objects

In most cases For..in is not harmful when iterating objects;

The problem arise when we inherit properties from the prototype;

Always check if the property exists in the instance before accessing it;

var User = function(uname){ this. Username = uname; return this;}User.prototype = { isDeleted:true}var usr = new User(‘Test’);for (var prop in User()) { // outputs Username // outputs isDeleted}

var User = function(uname){ this. Username = uname; return this;}User.prototype = { isDeleted:true}for (var name in username ) { if (username.hasOwnProperty(name) ) { // outputs Username }}

Function and Object Scope in JavaScript

Variable scope visible in the function;

All internal closures or functions will see the defined variables in the parent function scope;

function login() { var user = "test", isWrongCaptcha = true; if (isWrongCaptcha) { var timeToWait = 10; console.log( "Waiting " + timeToWait + " minutes" ); internal_log_in(); } function internal_log_in() { //The chew function also has access to the //timeToWait variable because it is part of the //eat function's scope console.log("After waiting " + timeToWait + " minutes, " + "I am going to login to the system"); }} login();//Waiting 10 minutes//After waiting 10 minutes, I am going to login to the system

Not aware of JSLint

JSLint is a static code analysis tool used in software development for checking if JavaScript source code complies with coding rules;

Provided primarily as an online tool, but there are also command-line adaptations;

http://www.javascriptlint.com/online_lint.php

Solution structure

Large scale JavaScript development involves different source types and formats; Presentation code;

Proxy code;

Third party libs;

Solution structure is tightly coupled with the solution architecture approach;

Physical structure should match the solution architecture abstraction;

Solution structure

/scripts /utils

/controllers

/models

/modules

/bootstrappers

/libs

/components

/external

/content /images

/css

/media

/scripts Development helpers

Proxy classes to the server methods

Models used for the client and server side

Modules per functionality

Application/module/plugin initializers

/libs Custom developed components

External libraries

/content /images

/css

/media

Solution architecture

Plan before execute;

Questions to be answered before the design: What will be reused?

How many modules depend on other modules?

Are your module sandboxed?


Break your application into small single-purpose parts - modules;

Module pattern gives you implementation privacy, state and code organization;

Provide a way to handle private and public methods and variables;

Protects the code to leak into the global namespace;


namespace.modulename = function(module) {

var privateVar = 'some data';

module.init = function(){

};

module.doSomething = function(){

internalDoSomething();

};

function internalDoSomething(){

};

return module;

}(namespace.modulename || {});


In some point there will be a need to establish module communication;

In order to avoid tight coupling we can utilize the mediator pattern;

The mediator pattern encapsulates how a set of modules interact;


Utilized via Pub/Sub;

Modules communicates via message publishing;

;(function ($) { var o = $({}); $.subscribe = function () { o.on.apply(o, arguments); }; $.unsubscribe = function () { o.off.apply(o, arguments); }; $.publish = function () { o.trigger.apply(o, arguments); };} (jQuery));

$.subscribe('namespace/action', function (data) {

alert(data);});

$.publish('namespace/action', 'data')


Wrapping it all together;

The modules publish events which inform the application that something is happening;

The modules in the system are subscribed to certain events;

The mediator enables the modules to communicate via the PubSub mechanism;

Product modules

Utilizing the module pattern;

JavaScript coding pattern;

Module pattern implementation with anonymous closures;

Should be considered: Every module should be part of a namespace;

Every module can contains sub modules;

What will be the global import of the module;

What will the module export;

Product modules

var namespace.module = (function (import) {var me = {};// private propertyvar somePrivateVar = 'Test data';// public propertyme.publicProperty = 'Public data';// private methodfunction privateMethod() {

somePrivateVar = 'executed pvt method';}// publicmethodme.publicMethod = function () {

return me.publicProperty;};// the module exportreturn me;

}(GLOBAL_IMPORT));

Product modules

Module inheritance can be done with module import;

namespace.module = (function (baseModule) {var me = {};// inherit the methods and propertiesfor (key in baseModule) {

if (baseModule.hasOwnProperty(key)) {me[key] = baseModule[key];

}}

var base_publicMethod = baseModule.publicMethod;

// public method overrideme.publicMethod = function () {

return base_publicMethod();};// the module exportreturn me;

}(module));

Dependency management

Which scripts should be loaded before initializing the modules;

Dependency management can be solved by using script loaders: RequireJS;

LABjs;

Yepnope;

General idea is that your module will not be loaded/executed until the required dependencies are not loaded;

Dependency management

$LAB .script("framework.js").wait() .script("plugin.framework.js") .script("myplugin.framework.js") .wait(function(){ myplugin.init(); framework.init(); framework.doSomething(); });

yepnope({ test : IsAdminUser, yep : 'normal.js', nope : ['polyfill.js', 'wrapper.js']});

define(["require", "./relative/name"], function(require) { var mod = require("./relative/name");});

UI Components

Build your UI components in jQuery plugin fashion;

jQuery plugin pattern is well known and understood by most of the UI developers;

Offers simple implementation syntax and offers extensibility;

UI Components

$.fn.pluginName = function(options){ // Create some defaults, extending them with any options that were provided var settings = $.extend( { 'location' : 'top', 'background-color' : 'blue' }, options);

// return the object back to the chained call flow return this.each(function() // This is the main processor // function that executes on // each selected element // (e.g: jQuery("div")) { var $this = $(this); alert($this); });};})(jQuery);

// usage$(document).ready(function() { // create a new instance of the plugin $(‘selector’).pluginName(options);});

Event Driven Messaging

Allow communication between modules via event publishing managed by pub/sub component;

Each module can publish events, subscribe and unsubscribe to events;

Event Driven Messaging

app.usermodule = (function () {var me = {};

me.onNewFriendNotificaion = function(notification){

alert(notification.from);};

me.init = function(){$.subscribe('on-new-friend-

notificaion', me.onNewFriendNotificaion);};

me.destroy = function(){$.unsubscribe('on-new-

friend-notificaion', me.onNewFriendNotificaion);

};

return me;}());

app.streammodule = (function () {var me = {};

me.post = function(){// do some client logic and

notify the other modules$.publish('on-new-friend-

notificaion', { from:'user' });};

return me;}());

Application routing

Managing navigation between application parts and pages;

Useful for: Centralizing navigation;

Uri history;

Navigation logging;

Application routing

<div id="container"> <div id="main"></div> <ul id="link"> <li> <a href="#/form">Form!</a> </li> <li> <a href="#/redirect">Redirect!</a> </li> <li> <a href="#/">Back</a> </li> </ul></div>

;(function ($) { var app = $.sammy('#main', function () { this.debug = true;

this.get('#/', function () { this.app.swap('Click form!'); }); this.get('#/redirect', function () { this.redirect('#/'); }); this.get('#/form', function () { this.partial('files/form.html'); }); }); $(function () { app.run('#/'); });})(jQuery);

Localization

String localization;

Dates, times, numbers, and currencies;

Use jQuery Globalize plugin for Dates, times, numbers, and currencies;

Localization

Store string resources in JSON format so they would be native to client;

Server string resources per culture;

Build language manager for the string resources;

Load the JSON resources into the language manager;

User the language manager to translate plugins, DOM elements and strings;

Logging

Useful for tracking modules state, variables and processes while in development;

Natively supported in all of the new modern browsers;

Use an existing logging framework or wrap your logger around the existing browsers logger;

Logging

var logger = function(){var logger = {};window.onerror = function(message, file, line) {

logError(file + ':' + line + '\n\n' + message);};logger.log = function(message){

logError(message);};function logError(message){

if(console && console.log){console.log(message);

}};return logger;

}();

Enterprise js pratices

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