Book Image

Opa Application Development

By : Li Wenbo
Book Image

Opa Application Development

By: Li Wenbo

Overview of this book

Opa is a full-stack Open Source web development framework for JavaScript that lets you write secure and scalable web applications. It generates standard Node.js/MongoDB applications, natively supports HTML5 and CSS and automates many aspects of modern web application programming. It handles all aspects of web programming written in one consistent language and compiled to web standards.Opa Application Development is a practical,hands-on guide that provides you with a number of step-by-step exercises. It covers almost all aspects of developing a web application with Opa, which will help you take advantage of the real power of Opa, as well as building a secure, powerful web application rapidly.Opa Application Development dives into all concepts and components required to build a web application with Opa. The first half of this book shows you all of the basic building blocks that you will need to develop an Opa application, including the syntax of Opa, web development aspects, client and server communication and slicing, plugin, database, and so on. By the end of the book you will have yourself created a complete web application along with a game: Pacman!
Table of Contents (18 chapters)
Opa Application Development
About the Author
About the Reviewers

Client and server communication

Opa provides three primitives for communicating between clients and the server: session, cell, and network. We can use these three primitives to exchange messages between clients and servers.


A session is a one-way asynchronous communication between the client and the server. A session can be created on a server or on a client, and can be shared between several servers.

To create a session, use either Session.make or Session.NonBlocking.make. The Session.make function creates a session that handles all messages in the background, but only one message at a time. This ensures absolute consistency on the state of the session, but may not be appropriate for all applications.

In contrast, the Session.NonBlocking.make function creates a session that can handle any number of messages simultaneously. This ensures maximal responsiveness, but the message handler cannot be certain that it is holding the latest value of the state. Let's have a look at how Session...