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

Broadcasting and receiving messages

What is left for us to do is to connect the model and the view. There are two distinct functions that we need to accomplish.

We must broadcast the current user's message when the Post button is clicked on or when Enter is pressed in the text field. We must also display new messages as they arrive.

Let's first have a look at how we broadcast the user's message when they press Enter:

<button class="btn btn-primary"
function broadcast(user)(_){
  text = Dom.get_value(#entry);
  Model.broadcast(~{user, text});

When the user presses Enter, the broadcast function will be invoked. In this function, we first get the user's input using Dom.get_value, and then we broadcast the message in the second line by calling the broadcast method in the module Model. Finally, we clear the content of the input field. That's all it takes to broadcast the message to all the connected clients. Now...