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Showing posts from April, 2019

Basic commands on MongoDB.

This blog will include the basic commands on MongoDB including the  'CRUD' operations. To gain access to MongoDB open up the command prompt and run the command  'mongod'   to start the server, and open up a separate command prompt and run the command  'mongo'   to access the MongoDB. Show all the available databases. Create new database. In this example a new database called  'mycustomers'  has been created. Once a database is created and if it does not have data, that database will not be visible when   'show dbs'   command is used. Show the current working databases. To display the current working database  'db'  command is used. Since the working database is   'mycustomers' ,  'db' command results mycustomers. Adding a collection to the database. Displaying the collection of the database. Deleting the coll...

Introduction to MongoDB

MongoDB is a No-SQL database. There are several types of No-SQL databases. Specifically MongoDB is a document database. All data/records are stored as documents. The data is stored using JSON (JavaScript object notation) like syntax. No-SQL databases are much different from relational databases like MYSQL where all the relations are being mapped,figuring out the exact schema including what table, fields, data type of fields is used  etc.. But in No-SQL the structure of the database/collection is planned but no need to predefined the structure before building the application. Advantages of MongoDB. High scallability.                    MongoDB is a horizontally scaled so when there is large amount of data it can be distributed to several machines. Faster.                     Since MongoDB is a document oriented database it is easy to access documents by in...

Basic concepts on ReactJS

Props and State. Props and state are the two basic ways to handle data in ReactJS.  Props are used to pass data and behaviors from container components to child components. Props are read only. State is used to keep data which can be updated. State is read write enabled. State. State is basically available through  'this.state', which is by default is null. Whenever the state changes on a component the component will  automatically re-render and update DOM (Document Object Model) if there are any changes else the DOM will not get touched at all. Using state. To change the state setState() method can be used. Since setTimeOut() method is used in the bellow example after a second (1000ms)  'Will'   will be changed to  'Bob'.   Changing the state using  'setState()' If the component has an internal value that does not effect the application state is appropriate. A side from that props can be used. Props. Pro...

Introduction to ReactJS

React is an open source front-end (JavaScript) library developed  and maintained by Facebook and Instagram for building fast and interactive user interfaces. Why ReactJS? In 2009 Facebook was using traditional data flow as the back-end. Therefore to get new updates the entire page had to be reloaded. In terms of initial data, real-time data and user data was flowing from different sources. Then the data was accordingly passed to the dispatcher, store and ultimately view. If there was any changes in the back-end in order  to reflect the changes on the view the entire  page had to be refreshed. This was not user-friendly. Drawbacks of traditional data flow. Uses DOM (Document Object Model). More memory consumption. Slow performance. With use of React the entire application is divided in to various components. When new data is added it will automatically update that component whose state has actually changed without reloading the entire pa...