Thursday, February 26, 2015

How to structure you JS application

According to my reasearch which I was doing in past few months I got to some conclusions on how to structure your application for best code reusability.

Several patterns come to my mind, Module, Namespace, immediate functions, returning objects, using subobjects, using capitalized letters for functions/variables as "Constants", function scope and making accessor methods, JS constructors, using Yuidoc and Jasmine for better code quality.

Download the code from here: https://github.com/bluePlayer/practices/tree/master/AppStructure

Here is roughly what I am thinking about:

var externalJSLibrary = {},
    jquery = {},
    extJS = {},
    expressJS;

window.APP = window.APP || (function (wdo, lib1, lib2, lib3) {'use strict';
    var version = "1.0.0",
        config = {},
        parent = null,
        jqueryObj = lib1,
        extJSObj = lib2,
        expressJsObj = lib3,
        windowDocumentObject = wdo,
        MY_APP_NAME = "MyJSApplication",
        MY_EXCEPTION_MESSAGE = "My exception message",
        MY_APP_CONSTANT = "some message";

    return {
        Exceptions: {
            MyFirstException: function () {
                return {
                    message: MY_EXCEPTION_MESSAGE,
                    name: "MyFirstException"
                };
            }
        },

        Constants: {
            MY_APP_NAME: function () {
                return MY_APP_NAME;
            },
            MY_APP_CONSTANT: function () {
                return MY_APP_CONSTANT;
            }
        },

        Events: {
             keyDownEvent: function (event) {
                 // do some stuff when some key is pressed down on 'keydown' event.
             },

             keyUpEvent: function (event) {
                 // do some stuff when some key is released on 'keyup' event
             },

             keyPressEvent: function (event) {
                 // do some stuff when 'keypress' event was detected
             }
        },

        initApp: function (someObject, config) {
            var i;

            for (i in someObject) {
                if (someObject[i] !== null && typeof someObject[i] === 'object') {
                    if (someObject[i].hasOwnProperty('init')) {
                        someObject[i].init(config);
                    }
                    parent.initApp(someObject[i], config);
                }
            }
        },

        namespace: function (nsString, newObjectDefinition) {
            var parts = nsString.split('.'),
                helperObject = {},
                that = this,
                i = 0,
                field = {};

            if (parts[0] === that.Constants.MY_APP_NAME()) {
                parts = parts.slice(1);
            }

            for (i = 0; i < parts.length; i += 1) {
                if (that[parts[i]] === undefined) {
                    for (field in newObjectDefinition) {
                        if (newObjectDefinition.hasOwnProperty(field)) {
                            helperObject[field] = newObjectDefinition[field];
                        }
                    }
                    that[parts[i]] = helperObject;
                }
                that = that[parts[i]];
            }
            return that;
        },

        customFunction: function (a, b) {
            if (b < 0) {
                throw new parent.Exceptions.MyFirstException();
            } else {
                return 0;// do some stuff with a and b
            }
        },

        doSomeStuffWithJquery: function (someUrl) {
            jqueryObj.ajax({
                url: someUrl,
                xhrFields: {
                    withCredentials: true
                }
            });
        },

        doSomeStuffWithExtJS: function () {
            extJSObj.drawGraph();
        },

        doSomeStuffWithExpressJS: function () {
            expressJsObj.connectWithNodeJS();
        },

        init: function (configObject) {
            config = configObject;
            parent = this;
            parent.initApp(parent, config);
        }
    };
    }(window.document, jquery, extJS, expressJS));

window.APP.namespace('MySubObject', (function (lib) {'use strict';
    var config = {},
        parent = null,
        someLibrary = lib,
        MY_CONSTANT = "my constant",
        MY_EXCEPTION = "my exception";

    return {

        Exceptions: {
            MyNewException: function () {
                return {
                    message: MY_EXCEPTION,
                    name: "MyNewException"
                };
            }
        },

        Constants: {
            MY_CONSTANT: function () {
                return MY_CONSTANT;
            }
        },

        name: "MySubObject",

        myCustomFunction: function () {
            // do some stuff
        },

        init: function (configObj) {
            config = configObj;
            parent = this;
        }
    };
    }(externalJSLibrary)));

window.document.addEventListener("DOMContentLoaded", function (event) {'use strict';

    var myApp = window.APP;

    myApp.init({
        "event": event,
        otherConfig: {}
    });

    window.document.addEventListener('keydown', myApp.Events.keyDownEvent);
    window.document.addEventListener('keyup', myApp.Events.keyUpEvent);
    window.document.addEventListener('keypress', myApp.Events.keyPressEvent);

    });

"JavaScript Patterns" - book review

Hello. In this post I will share my thoughts on a book called "JavaScript Patterns" written by Soyan Stefanov. Published in 2010 this book in about 210 pages covers the most important patterns that you can use in JavaScript to ease you work with this language. My guess is that this book is not for beginner JavaScript programmer, but you can always read this great book by Douglas Crockford, "JavaScript: The Good Parts" as an intro to JavaScript. These two books go hand in hand. Check my other book review here: http://tunephp.blogspot.com/2014/11/javascript-good-parts-book-review.html
If you really want to learn proper JS programming read both of them, first "JS the good parts" and then "JS Patterns" and try some programming practices in Firefox/Firebug.

The book has 8 chapters and has lot of useful code snippets you can use in building your brand new JavaScript application.

  1. Intruduction. Explains basic concepts of JS, like there are no classes in JS, everything is a object including, functions, arrays, objects etc... It also notes that you can use strict ("use strict", ECMAScript 5) mode, a modification of JS that removes some of the bad parts in JS. This chapter also introduces JSLint and the Console as debugging tools. You should always check your code with JSLint.
  2. Essentials. This chapter covers one of the main drawbacks in JS, and those are global variables. It also gives some tips how to avoid using too many globals, how to use "for", "for in" loops, avoiding implied typecasting with "==" sign, number conversions with parseInt() and parseFloat(), writing proper code, indentation, writing comments and using Yuidoc and JSLint.
  3. Literals and Contructors. It covers Object literal ({}) notation, JS constructors and naming convention for them and how to avoid problems using constructors. Array literals, check for "Arrayness" (arrays are objects in JS), working with JSON, regular expressions, primitive wrappers and throwing Errors/Exceptions.
  4. Functions. Covers function decalrations vs function expressions. Variable hoisting, function scope, function callbacks, returning functions, self defining functions, immediate functions and couple of useful tricks like memoization, curry, init-time branching etc... Probably the most important chapter in the book, you must not miss it as functions are the hearth of JavaScript.
  5. Object Creaing Patterns. Some object creating patterns like namespace patters(there is a very useful function for creating a tree of subobject, you can use it in your project.), private members, how to achieve real privacy in JS, Module pattern, Sandbox patterns, static members, JS "Constants", Chaining pattern etc... This chapter gives you better idea how to structure your code so that your project doesn't have trouble in the end.
  6. Code Reuse Patterns. Classical vs Prototypal inheritance patterns. You should avoid Class inheritance in JS since it is just a "syntaxic sugar", and always use Prototypal inheritance. This chapter also mentions some useful code reuse techniques, like borrowing methods, copying properties, some Class patterns etc...
  7. Design Patterns. This chapter covers how to code basic software engineering patterns in JavaScript, probably a chapter you don't want to miss. Singleton, Factory, Iterator, Decorator, Strategy, Facade, Proxy, Mediator and Observer. 
  8. DOM and Browser Patters. Covers some tools/concepts/patterns that can be used in a browser, like how to manipulate DOM tree, event handling, long running scripts, Ajax alikes, JSNOP, combining JS scripts, minifying, Loading techniques and preloading.
 So yes, this book cover very useful features of JavaScript and how to use them in browser. If you really want to become a web dev. this is the right book for you.

There are similarities with "JavaScript: The Good Parts" in the beginning, I felt like I was reading Doug's book again, but that is ok. It has lot of code and it is well explained so my grade for it is 4.5/5. Defineitely a book you should read.

Monday, February 23, 2015

Introducing new project called ZadachiJS

In the past few weeks I have been working on a new project called ZadachiJS. It is adapted for Macedonian public and the docs are written in Macedonian using english letters. It is basically a web application that has no GUI and all output is sent to the console, ofcourse the output is in Macedonian. It contains programming practices which could be made in any programming language and it is based on a book called „Збирка Алгоритми и Програми“, од Ѓорги Јованчевски, Билјана Стојчевска и Невена Ацковска or in english, "Collection of Algorithms and Programs" written by Gyorgy Yovanchevsky, Bilyana Stoychevska and Nevena Atckovska. I couldn't find english version of it, but I could in Macedonian. Not sure if there is going to come an english version. So if you want to understand this project better learn Macedonian, because probably I won't find time to translate it in English, who knows.

Збирка Алгоритми и Програми
Збирка Алгоритми и Програми

The JavaScript part consists of one global object called Zadachi and all other stuff are inside of it.
You can browse the code here: https://github.com/bluePlayer/practices/tree/master/ZadachiJS
or check the demo here: http://jspractices-blueplayer.rhcloud.com/Zadachi and the docs here: http://jspractices-blueplayer.rhcloud.com/Zadachi/docs

Thursday, February 19, 2015

New location for JavaScript practices.

Check this link for my new page regarding JavaScript demos.

http://jspractices-blueplayer.rhcloud.com/

GitHub: https://github.com/bluePlayer/practices

Note: If some of the demos is unavailable write me on this post or an email, because openshift sets the process to idle state if the page is not accessed often.

Wednesday, January 28, 2015

JavaScript "constants"

I did a bit of research about constants in JavaScript. Well guess what, there are no constants in JavaScript. :)

So how do you implement "constants" with JavaScript patterns and syntax?

Note: The next text might require more readings but if will help you learn lot of JavaScript basics. Probably you will never have to use this code, since existing JS librarires have already solved this issue somehow.

Constants are important concept of every programming language and definetelly you should use them whenever possible. For example let just say you have an error message that needs to be printed in the output field from several places in your code. How are you sure that each time you write that string of message is written without missing letters? Sometimes you are tired, sometimes you rush and therefore errors are inevitable. So to prevent this you create a constant that contain that string and use the constant instead of writing the string.

Example constant: CANNOT_DIVIDE_BY_ZERO = "Cannot divide by zero!";

I have been developing a practice application which you can access live here: http://jspractices-blueplayer.rhcloud.com/Calculator/ and the docs are here: http://jspractices-blueplayer.rhcloud.com/Calculator/docs
Also you may preview the HTML/JavaScript code here: https://github.com/bluePlayer/practices/tree/master/CalculatorJS.
The code also passes JSLint test, with only "jslint browser: true" option.

There are two important functions which you should check, Constants() and namespace().
Constants() is a constructor function and namespace() creates subobject of the main application object called window.APP.
Lets start with namespace() function. It recieves two parameters, first the name of the subobject that will be created and second is the configuration object which contains necessary properties and methods that will be contained in this new subobject. namespace() creates new subobject Constants using the new keyword, secondly creates constMap subobject which will contain accessible keys for each of the constants.

Example:

window.APP.namespace('Trigonometry', (function () {
    return {
        PI: 3.14,
        doSomeStuff: function () {

        }
    }
}()));

This example creates Trigonometry subobject of window.APP and Trigonometry contains two subobjects, Constants with methods, get(), set(), isDefined() and list() and constMap which has one key/value, PI: "PI" and ofcourse the function doSomeStuff() which does nothing.

So with my solution you can create immutable constants by just passing key/value pair (key must be all capitalized letters) and the code will create it for you. Well if we create a PI constant how do we get the value? The solution is straight forward but it looks very ugly and big.

Example:

console.log(window.APP.Trigonometry.Constants.get(window.APP.Trigonometry.constMap.PI));
// prints 3.14

Alternatively you can pass the name of the constant if you know it:

console.log(window.APP.Trigonometry.Constants.get("PI"));

hahah :D

To improve this solution a bit I created an application wide function in APP namespace called getConst(). You send the path of the constant in string format.

Example:  

console.log(window.APP.getConst('APP.Trigonometry.PI')); // prints 3.14

What happens in this function is parsing the string parameter and getting to the constant value trough the application tree. But this solution is against the "Constants" concept. Either I should be careful to write that string parameter properly or I should create a variable/property inside APP to contain that string and then use it in the above example, like so:

window.APP = window.APP || (function () {
    var TRIGONOMETRY_PI =  'APP.Trigonometry.PI';
    return { 
        getConst: function (constantPath) {
            // code
        },
        doSomeStuff: function () {
               console.log(this.getConst(TRIGONOMETRY_PI)); 
        }
    }
}()));

window.APP.doSomeStuff(); // prints 3.14


So this brings us to the best solution to the problem, and that is creating variables with capitalized letters in closure and then using capitalized accessor methods for them.

Example: I will create GRAVITY = 9.8 constant in new subobject of APP, called Physics.
window.APP.namespace('Physics', (function () {
    var GRAVITY = 9.8;
    return {
          GRAVITY: function () {
               return GRAVITY;
         }
    };
}()));

console.log(window.APP.Physics.GRAVITY()); // prints 9.8

This will create subobject Physics in window.APP and it will contain constMap object with one key/value pair, GRAVITY which is function(). I changed namespace() function to create function in constMap if the capitalized key contains value of a function instead of a value.  If I just send this key/value pair: GRAVITY: 9.8, the namespace() function would have created key/value pair in constMap, like so: GRAVITY: "GRAVITY" and you have to access constant's value using the long statement in the previous examples.

To clear things up, you don't even need to create Constants() constructor in your application, you can use variable with closure and accessor methods with capitalized names to represent constants. I created this constMap subobject just to separate constants from other properties/methods in a given object. You don't even need it.

Note: there are some rummors that ECMAScript 7 or was it 6, will contain const keyword. Until then you can use capitalized variable and methods with closure to represent "constants".

If you have any thoughts on the topic, let me know.


Thursday, January 8, 2015

JavaScript Patterns - practice application

Hello. In this post I will explain some JavaScript patters using a script I made.
I have being reading this book: JavaScript Patterns by Stoyan Stefanov, and I covered half by now.

 You can download the script from this link https://github.com/bluePlayer/practices/tree/master/CalculatorJS

I also wrote comments for each property/method/object/module in YuiDoc format and generated in Java style, documentation using YuiDoc Node.js extension. For more info check this link: http://yui.github.io/yuidoc/

So the name of my application is APPLICATION and it is written with capitalized letters because it is global variable. Some JS coding convetions say that you should write constants and globals with capitalized letters because it is easier to distingush from other properties/variables.

It is always good to initialize main application object if it doesn't exist, or prevent initiazlization if it already exist:

var APPLICATION = {};
if (typeof APPLICATION === "undefined") {
    var APPLICATION = {};
}
// shorter
var APPLICATION = APPLICATION || {};

While I was reading "JavaScript Patterns" it mentioned a general namespace function which enables you to create objects and subobjects by just sending dot notated string, like this: "my.new.object".
I made some improvements to this function and added it as a part of the application's namespace, like this:

APPLICATION.namespace = function (nsString, newObjectDefinition) {
    var parts = nsString.split('.'),
        parent = this,
        newObject = {};
       
    newObject.Constants = new this.Constants();
    newObject.constMap = {};
   
    if (parts[0] === this.getName()) {
        parts = parts.slice(1);
    }
   
    for (var i = 0; i < parts.length; i += 1) {
        if (typeof parent[parts[i]] === "undefined") {           
            for (var property in newObjectDefinition) {
                if (property === property.toUpperCase()) {
                    newObject.Constants.set(property, newObjectDefinition[property]);
                    newObject.constMap[property] = property;
                } else {
                    newObject[property] = newObjectDefinition[property];
                }
            }
            parent[parts[i]] = newObject;
        }
        parent = parent[parts[i]];
    }   
   
    return parent;
};


I added a second parameter which adds functionality to the last object created in the tree. So if the fisrt parameter is string: "my.new.object", the function will create three objects, my, new and object in the APPLICATION's tree and object will be initialized with properties and functions from the second parameter. I also added two more subobjects inside every newly created object, so my, new, object will have Contants and constMap objects. Constants is object which gets created with Constants() constructor (from APPLICATION) and it contains, set(), get(), isDefined(), list(). On the other hand constMap contains the keys for calling constants using the get() function. So to get a constant value you should do this:

var myVar = APP.subModule.Constants.get(APP.subModule.constMap.CONST_NAME);

Note: This looks quite clumsy and big. Lot of letters to write. Perhaps it will be easier to write in some JS IDE like WebStrom. Anyway, at the time of writing this code I realised there is a place for improvement. Maybe there should be one general get() function for constants in the application.

As you can see from the application I use namespace pattern. All constructors, methods, events, properties, submodules should be part of one general object. Also I have submodules like, Main, Trigonometry, EventFunctions  and all related properties or methods are kept in its own submodule. This is called module pattern.

What if I want to add static properties? Well you can do it easily by just adding a new property to a given object or subobject. You can also use prototype part of the object and it will be inherited.
example:

var MyObject = function () {};
MyObject.name = "TunePHP";
var newObject = new MyObject();
typeof newObject.name === "undefined" //true
MyObject.prototype.name = MyObject.name;
console.log(newObject.name); // "TunePHP";

It is always useful to have a main init() method for the whole application, where you will initialize all necessary objects/variables/properties after the page has loaded.

Here is the complete code I wrote. Let me know your thoughts.

var APPLICATION = APPLICATION || {
    name: "Calculator",
    version: "1.0.0",
    Constants: function () {},
    namespace: function () {},
    getName: function () {
        return name;
    },
   
    init: function (config) {
        try {
            this.Calculator.Main.currentState = this.Calculator.Main.Constants.get(this.Calculator.Main.constMap.STANDARD);
            this.Calculator.Trigonometry.currentAngleFormat = this.Calculator.Trigonometry.Constants.get(this.Calculator.Trigonometry.constMap.DEGREES);
            return this;
        } catch (error) {
            console.log(error.message);
            return false;
        }
    }
};

APPLICATION.Constants = function (constMapObject) {
    var constants = {},
        ownProp = Object.prototype.hasOwnProperty,
        allowed = {
            string: 1,
            number: 1,
            boolean: 1
        },
        prefix = (Math.random() + "_").slice(2);
       
    return {
   
        set: function (name, value) {
            if (this.isDefined(name)) {
                return false;
            }
            if (!ownProp.call(allowed, typeof value)) {
                return false;
            }
                   
            constants[prefix + name] = value;
            /**
             * @todo use constMapObject to create new constant key in the given constants map object.
             */
            return true;
        },

        isDefined: function (name) {
            return ownProp.call(constants, prefix + name);
        },
       
        get: function (name) {
            if (this.isDefined(name)) {
                return constants[prefix + name];
            }
            return null;
        },
       
        list: function () {
            var index = 0,
                newStr = "";
               
            for (constant in constants) {
                index = constant.indexOf('_');
                newStr = constant.substr(index + 1);
                console.log(newStr + ": " + constants[constant]);
            }
        }
    };
};

APPLICATION.namespace = function (nsString, newObjectDefinition) {
    var parts = nsString.split('.'),
        parent = this,
        newObject = {};
       
    newObject.Constants = new this.Constants();
    newObject.constMap = {};
   
    if (parts[0] === this.getName()) {
        parts = parts.slice(1);
    }
   
    for (var i = 0; i < parts.length; i += 1) {
        if (typeof parent[parts[i]] === "undefined") {           
            for (var property in newObjectDefinition) {
                if (property === property.toUpperCase()) {
                    newObject.Constants.set(property, newObjectDefinition[property]);
                    newObject.constMap[property] = property;
                } else {
                    newObject[property] = newObjectDefinition[property];
                }
            }
            parent[parts[i]] = newObject;
        }
        parent = parent[parts[i]];
    }   
   
    return parent;
};

 APPLICATION.namespace('Calculator', {
   
});

APPLICATION.namespace('Calculator.Main', {
   
    STANDARD: 1,

    SCIENTIFIC: 2,

    PROGRAMMER: 3,
   
    currentState: null,

    currentValue: 0,

    memoValue: 0,
   
    digitGrouping: false,
   
    historyPanel: false,
   
    unitConversionPanel: false,

    dateCalculationPanel: false,

    changeState: function (event) {
        /**
         * @todo currentState = event.newState;
         */
    },
       
    showHistoryPanel: function (event) {
        /**
         * @todo
         */
    },
       
    showUnitConversionPanel: function (event) {
        /**
         * @todo
         */
    },

    showDateCalculationPanel: function (event) {
        /**
         * @todo
         */
    }
});

APPLICATION.namespace('Calculator.Trigonometry', {

    DEGREES: "degrees",
   
    RADIANS: "radians",

    GRADS: "grads",
   
    currentAngleFormat: null
});

APPLICATION.namespace('Calculator.EventFunctions', {

    pressZero: function (event) {
   
    },

    pressOne: function (event) {
   
    },

    pressTwo: function (event) {
   
    },
   
    pressSum: function (event) {
   
    },

    pressSubtract: function (event) {
   
    },
   
    pressMultiply: function (event) {
   
    },

    pressDivide: function (event) {
   
    }
});

APPLICATION.init({});

Friday, December 19, 2014

Assasins Creed: Pirates HTML5/JS/WebGL demo

Another demo that caught my eye is Assasins Creed: Pirates Demo made by the IE engineering team, with HTML5, JavaScript, WebGL and more specifically Babylon.js Here is a web page that explains how to start working with Babylon.js and create 3D virtual worlds in a browser.


I played the demo several times in Firefox 34 and I can say it looks fantastic coupled with nice pirate music. There are nine weather conditions between you can choose to play, and each has its own specifics, like day or night, rainy or sunny etc... Use A, D to keys to turn the ship left or right and W, S to speed up or slow down. Use V to switch camera from third person view to first person view and vice versa. Use mouse to rotate the camera around the ship.

Note: To enable and use these new browser technologies you must have IE11 and Windows 7 Service Pack 1 or other advanced browser like Google Chrome, Opera and Firefox. Safari 5.1.7 does not support WebGL.

More info here: https://www.modern.ie/en-us/demos/assassinscreedpirates
Other IE demos: http://ie.microsoft.com/testdrive/Default.html
Babylon.js Challenge: http://www.babylonjs.com/cyos/acpr/#OKULH#1 

Assasins Creed: Pirates Demo
Assasins Creed: Pirates Demo
Intro Comic
Intro Comic
Controls
Controls
WebGL lighting effect
WebGL lighting effect
Beautiful environment
Beautiful environment
I have won the game
I have won the game
First person view. Beautiful foggy effect
First person view. Beautiful foggy effect
Moon shines
Moon shines
Rotate the camera with the mouse
Rotate the camera with the mouse
Rotate the camera with the mouse
Rotate the camera with the mouse