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Node.JS - File operation examples

File operations are very common requirements and I thought of providing some simple examples in Node.js. The Node.js provide a module called "fs" which is having all necessary functions for performing file operations. Let's start with very simple examples. Audience The examples are very basic and focused for beginners. Reading and Writing Files The file system module provide a synchronous and asynchronous functions for reading and writing a file. Example for reading a file using synchronous function fs.readFileSync. const fs = require('fs'); const information = fs.readFileSync('files/file1.txt', 'utf8'); console.log(information); Example for reading a file using asynchronous function fs.readFile. const fs = require('fs'); const information = fs.readFile('files/file1.txt', 'utf8', (err, information) => { if (err) { console.log('Error occured while reading a file'); return; }
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Meteor tutorial - Part II - Building mobile applications

In my previous blog post , I have explained basics of meteor. In this tutorial I am going to add mobile support to the existing meteor application. Installing mobile SDKs Before going to start we need to install IOS and android SDKs (Software development kit). Here I am installing SDKs for iOS. Please keep in mind this is one time process. For installing iOS SDKs, we need to invoke “meteor install-sdk ios”. The same way you can install android SKDs by invoking “meteor install-sdk android” command. Adding mobile platform support I am using already created application called “myapp” and going to add iOS platform support by invoking a command “ meteor add-platform ios ”. We can add android platform by invoking a command  “ meteor add-platform android ”. Running application on mobile emulator Once we add mobile platform then we can run our application by using real mobile device or emulator. I have added IOS platform to myapp already. Now I am going to run th

Meteor tutorial - Part I

What is Meteor? Meteor is a complete open source platform for building web and mobile application by using JavaScript. It is a combination of NodeJs, MongoDB and client side JavaScript. Installing meteor Meteor supports windows, linux and Mac operating systems. Invoke below command in terminal for installing meteor in mac operating system. Check below link for installing meteor on other operating systems. http://docs.meteor.com/#/basic/quickstart Creating an application The command “meteor create <<app_name>>” is used for creating new meteor application. I have created an app called “myapp” and will see how we can run the application. Running an application “meteor run” command is used for running meteor application. Internally it start a node js server and by default that will listen 3000 port number. Just make sure you are in project directory (myapp) before invoking run command. ' Other useful meteor commands Meteor provides lot of usefu

GRUNT – Cleaning and Minifying JavaScript Files

In this tutorial, we are going to create a NodeJS/Grunt project which has basically used for minifying many JavaScript files into one. The steps are, Step 1.  Install NodeJS latest version and refer “http://nodejs.org/download/” link for more information. Step 2.  If you are having any existing NodeJS instance then just update by using “npm update –g npm” command. I am having existing NodeJS instance and updated by invoking above command. Step: 3. Next, we need a Grunt command line interface (CLI) tools globally. It is a node.js module and needs to install by using a command called “npm install –g grunt-cli”. Step 4.  We need another component called grunt-init globally. It is also a node.js module and we can install it globally by invoking a command “npm install –g grunt-init”. Step 5.  Next, we need to create a new grunt project. I have created new folder called “Grunt-MinifyDemo” in “D“ directory and this is my project. Step

iOS - Simple to-do application development

After a long time, I had some good time to study native iOS development and developed simple to-do application by following a tutorial present in iOS developer library . The source code is available in  githup repository and don't worry about modifying the source code. Currently this application doesn't store our to-do items permanently. Probably my next change should be storing our to-do list in database. Now if you kill the application the data will be lost :)

JavaScript - An Example for Inheritance

Everyone of us know, Inheritance is a way to acquire properties and methods of another object. In other words it is a way to establish is-a relationship between two objects. The static languages by default provide some easier ways to achieve this. For an example, we have "extend" keyword in Java for extending other object. JavaScript is protypal inheritance language (class-free) means that objects can inherit properties from other objects. Let's see an example. Let's create a parent class for Animal /** * Animal - Constructor and parent class for all animals. * @param {Object} aType - Type of the animal * @param {Object} aName - Name of the animal */ function Animal(aType, aName) { this.type = aType; this.name = aName; } Animal.prototype.eat = function() { console.log('All animal will eat'); }; We have to do following steps for extending animal class. 1. Calling super class constructor from child class constructor. 2. Setting up prot

JavaScript - An example for Singleton pattern

The singleton pattern is a design pattern that restricts instantiation of the class to one object. This pattern is very handy when one object is enough for doing some operation across the entire system. Let's see an example. /** * Single global namespace for an entire application with lazy loading. * @Singleton pattern */ var PUS = PUS || {}; PUS = (function(){ //Private variables and methods var appVersion = 0.1, instance = null; function constructor() { console.log('Object has created'); return { getAppVersion : function() { return appVersion; } }; }; return { getInstance : function() { if(!instance) { instance = constructor(); } return instance; } }; })(); Here PUS object contains one public method called "getInstance". If we call PUS. getInstance() method, that will first check whether an object is already created or not. The object is already exists then will return the reference of an existing object, ot