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

Binding Node.js

Binding Node.js code is just as easy as binding JavaScript. Let's see an example: suppose we have written a function called calcMD5 in a Node.js file called test.nodejs. The function accepts a string and returns its MD5 hash value. The test.nodejs file contains the following code:

/** test.nodejs */
var crypto = require('crypto');
 * Calculates the MD5 hash value of a string.
 * @register {string -> string}
var calcMD5 = function(str){
    return crypto.createHash('md5').update(str).digest('hex');

As we can see from the preceding code, we bind Node.js in the same manner that we previously used to bind the client-side JavaScript code. We also invoke it in the same way:

/** 603.opa */
md5 = %%test.calcMD5%%("Hello Opa!");
println("MD5 value: {md5}");

And finally, we compile and run the application:

opa test.nodejs 603.opa --

The result is as shown in the following screenshot: