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  • Khóa học miễn phí PouchDB – Create Document nhận dự án làm có lương

    PouchDB – Create Document

    You can create a document in PouchDB using the db.put() method.

    Syntax

    Following is the syntax of using the db.put() method of PouchDB. You can store the document that is to be created in PouchDB, in a variable and pass as a parameter to this method. In addition, this method also accepts a callback (optional) function as a parameter.

    db.put(document, callback)

    Example

    Following is an example of creating a document in PouchDB using the put() method. The document we create should be of JSON format, a set of key-value pairs separated by comma (,) and enclosed within curly braces ({}).

    //Requiring the package
var PouchDB = require(''PouchDB'');

//Creating the database object
var db = new PouchDB(''my_database'');

//Preparing the document
doc = {
   _id : ''001'',
   name: ''Raju'',
   age : 23,
   designation : ''Designer''
   }
//Inserting Document
db.put(doc, function(err, response) {
   if (err) {
      return console.log(err);
   } else {
      console.log("Document created Successfully");
   }
});

    Save the above code in a file with name Create_Document.js. Open the command prompt and execute the JavaScript file using node as shown below.

    C:PouchDB_Examples >node Create_Document.js

    This creates the given document in PouchDB database named my_database, which is stored locally, displaying the following message.

    Document created Successfully

    Inserting a Document in a Remote Database

    You can also insert a document in the database that is stored remotely on the server (CouchDB).

    To do so, instead of database name you need to pass the path to the database where you want to create documents in CouchDB.

    Example

    Suppose there is a database named my_database in the CouchDB server. Then, if you verify the list of databases in CouchDB using the URL http://127.0.0.1:5984/_utils/index.html you will get the following screenshot.

    Inserting a Document in a Remote Database

    Now, if you click on the database named my_database, you will find an empty database as shown in the following screenshot.

    Empty Database

    Following is an example of inserting a document in a database named my_database that is saved in the CouchDB server.

    //Requiring the package
var PouchDB = require(''PouchDB'');

//Creating the database object
var db = new PouchDB(''http://localhost:5984/my_database'');

//Preparing the document
doc = {
   _id : ''001'',
   name: ''Raju'',
   age : 23,
   designation : ''Designer''
   }
//Inserting Document
db.put(doc, function(err, response) {
   if (err) {
      return console.log(err);
   } else {
      console.log("Document created Successfully");
   }
});

    Save the above code in a file with the name Remote_Create_Document.js. Open the command prompt and execute the JavaScript file using node as shown below.

    C:PouchDB_Examples >node Remote_Create_Document.js

    This creates the given document in PouchDB database named my_database which is stored in CouchDB, displaying the following message.

    Document created Successfully

    Verification

    After executing the above program, if you visit the my_database again, you can observe the document created as shown in the following screenshot.

    Remote Database Verification

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  • Khóa học miễn phí PouchDB – Overview nhận dự án làm có lương

    PouchDB – Overview

    This chapter provides a brief introduction to PouchDB along with its features and how it works.

    What is PouchDB?

    PouchDB is an open source in-browser database API written in JavaScript. It is modelled after &minuss; a NoSQL database. Using this API, we can build applications that work offline and online. It internally uses WebSQL and IndexedDB to store data.

    How Does it Work?

    In PouchDB, when the application is offline, the data is stored locally using WebSQL and IndexedDB in the browser. When the application is back online, it is synchronized with CouchDB and compatible servers.

    Using PouchDB, you can communicate with both local and remote databases seamlessly without noticing any difference.

    Features of PouchDB

    Following are the features of PouchDB −

    • Cross Browser − The API provided by PouchDB works the same in every environment, therefore, we can run a PouchDB application in various browsers.

    • Light Weight − PouchDB is a very light-weight API, it is also included easily just using a script tag.

    • Easy to Learn − If you have a prior knowledge of any programming language, it is easy to learn PouchDB.

    • Open Source − PouchDB is an Open Source Application and is available on GitHub.

    Advantages of PouchDB

    Following are the advantages of PouchDB −

    • Since PouchDB resides inside the browser, there is no need to perform queries over the network, this results in faster execution of queries.

    • You can synchronize the data with any of the supported server and by doing so you can run apps both online and offline.

    Browsers that Support PouchDB

    Following are the browsers that support PouchDB −

    • Firefox 29+ (Including Firefox OS and Firefox for Android)
    • Chrome 30+
    • Safari 5+
    • Internet Explorer 10+
    • Opera 21+
    • Android 4.0+
    • iOS 7.1+
    • Windows Phone 8+

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  • Khóa học miễn phí PouchDB – Home nhận dự án làm có lương

    PouchDB Tutorial

    PouchDB Tutorial







    PouchDB is an open source in-browser database API written in JavaScript. It is modelled after CouchDB − a NoSQL database that powers npm. Using this API, we can build applications that work offline and online. PouchDB uses WebSQL and IndexedDB internally to store the data.

    This tutorial discusses the basics of PouchDB along with relevant examples for easy understanding.

    Audience

    This tutorial has been prepared for beginners to help them understand the basic concepts of PouchDB. It will aid you to build applications which will work offline and online alike using PouchDB and CouchDB.

    Prerequisites

    The reader should have a basic knowledge of databases. It would be better to have a good command on programming languages, which are compatible with node.js such as JavaScript and CoffeeScript.

    Frequently Asked Questions about PouchDB

    There are some very Frequently Asked Questions(FAQ) about PouchDB, this section tries to answer them briefly.

    PouchDB is a JavaScript library that allows developers to create and manage databases directly in web browsers or in Node.js applications. It is designed to be lightweight, fast, and easy to use, providing a way to store and sync data locally on a user”s device, even when offline. PouchDB uses a NoSQL database model, similar to JSON (JavaScript Object Notation), making it flexible and well-suited for storing and querying structured data. It also supports features like replication, allowing data to be synchronized between multiple devices or with a remote server.

    PouchDB allows users to work offline by storing data directly on their devices. It creates a local database where data can be saved and accessed without an internet connection. When online, PouchDB synchronizes the local database with a remote server, ensuring that any changes made offline are replicated to the server. This enables users to access and interact with their data both online and offline, providing a seamless experience across different network conditions.

    PouchDB supports various data types, making it versatile for storing different kinds of information. Some of the common data types supported by PouchDB are as follows −

    • Strings − Textual data, such as names, descriptions, and messages, can be stored as strings in PouchDB.

    • Numbers − Numeric data, such as quantities, prices, and ages, can be stored as numbers in PouchDB.

    • Boolean − True/false values, which represent binary states like yes/no or on/off, can be stored as boolean data in PouchDB.

    • Arrays − Collections of related data, such as lists of items or sets of values, can be stored as arrays in PouchDB.

    • Objects − Complex data structures, consisting of key-value pairs, can be stored as objects in PouchDB.

    PouchDB and CouchDB are both databases that use similar technology, but they serve different purposes and have different use cases −

    • PouchDB − PouchDB is designed to run directly in web browsers and mobile devices, allowing developers to create applications that can work offline and sync data with a remote server when online. It is lightweight and optimized for use in client-side applications.

    • CouchDB − CouchDB, on the other hand, is a full-fledged database server that runs on servers or cloud platforms. It is designed for storing and managing large amounts of data, providing features like replication, clustering, and map-reduce queries. CouchDB is suitable for building server-side applications and back-end systems.

    Data in PouchDB is stored locally on the user”s device, such as a web browser or mobile device. PouchDB creates a local database that resides directly on the user”s device, allowing data to be stored and accessed without needing an internet connection. This local database functions similarly to other databases but is specifically designed to work offline.

    Users can interact with the data stored in PouchDB just like they would with any other database, but the data remains on their device until it is synchronized with a remote server. This local storage capability enables applications built with PouchDB to provide offline functionality, allowing users to work with their data even when they are not connected to the internet.

    PouchDB is seamlessly integrated into web applications, allowing developers to create offline-capable apps by storing data directly within the user”s web browser. Once initialized, PouchDB provides a local database where data can be stored and managed, enabling users to interact with the application even when offline. When the user reconnects to the internet, PouchDB automatically syncs the local data with a remote server, ensuring data consistency across devices. This implementation of PouchDB empowers developers to build strong web applications that provide a smooth user experience, regardless of network connectivity.

    The purpose of PouchDB”s “changes” API is to allow developers to listen for and respond to changes that occur in the database in real-time.

    Imagine you are watching a live sports game on TV. The “changes” API is like having a live feed of updates about the game. Whenever something happens in the game, like a goal being scored or a foul being called, you immediately see it on your screen without having to wait for a recap. Similarly, with PouchDB”s “changes” API, developers can receive instant notifications whenever new data is added, updated, or deleted in the database. This allows them to react to changes in real-time, updating the user interface or performing other actions as needed.

    SQLite and PouchDB are both databases, but they serve different purposes and work in different environments −

    • SQLite − SQLite is a relational database management system (RDBMS) that is generally used in server-side applications or desktop software. It is designed to store and manage structured data efficiently, making it suitable for applications that require complex queries and transactions. SQLite databases are often used in situations where data needs to be shared across multiple users or devices.

    • PouchDB − PouchDB, on the other hand, is a NoSQL database that is designed to run directly in web browsers or mobile devices. It is optimized for use in client-side applications, allowing developers to create applications that can work offline and synchronize data with a remote server when online. PouchDB is particularly well-suited for web applications that need to store and manage data locally on the user”s device.

    The latest version of PouchDB is 7.2.2. PouchDB releases new versions periodically to provide updates, bug fixes, and improvements to the library. These updates may include enhancements to performance, new features, and compatibility with the latest web technologies. It is important for developers to keep their PouchDB library up to date by installing the latest version to ensure their web applications are running smoothly and efficiently. Checking the official PouchDB website or repository can provide the most up-to-date information on the latest version and its features.

    PouchDB doesn”t have a strict maximum size limit for the database itself. However, the amount of data that PouchDB can store is ultimately limited by the available storage space on the device where it is running.

    Think of it like a storage box in your home: the maximum amount of stuff you can store in the box depends on its size. Similarly, the maximum amount of data PouchDB can store depends on the storage capacity of the device it is installed on, such as a web browser or mobile device.

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