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

Basic datatypes

Datatypes are the shapes of data manipulated by an application. Opa uses datatypes to perform sanity and security checks on your application. Opa also uses datatypes to perform a number of optimizations. There are three basic datatypes in Opa: integers, floats, and strings. Also, you can define your type with the keyword type:

type Student = {string name, int age, float score}
Student stu = { name:"li", age:28, score:80.0}

Actually, thanks to a mechanism of type inference, Opa can work in most cases even if you do not provide any type information. For example:

x = 10        // the same as: int x = 10
x = {a:1,b:2} // the type of x is: {a:int, b:int}

So in the rest of this chapter, we will not address type information before variable, but you should know what type it is in your mind. In actual coding, a best practice is to provide the datatypes of our main functions and to let the inference engine pick up the datatypes of all the local variables and minor functions.