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

Data structures

The only way to build data structures in Opa is to use records, which we will talk about later on. All other data structures, such as tuples and lists, are based on records. Opa provides different modules to help the user to manipulate lists and maps. Let's first have a look at records.


Simply speaking, a record is a collection of data. Here is how to build a record:

x = {} // the empty record
x = {a:2,b:3} //a record with field "a" and "b"

The empty record,{}, has a synonym, void, which means the same thing. There are a number of syntactic shortcuts available to write records concisely. First, if you give a field name without the field value, it means the value of this field is void:

x = {a}      // means {a:void}
x = {a, b:2} // means {a:void b:2}

The second shorthand we always use is the sign ~. It means if the field value is left empty, assign it with a variable having the same name as the field name:

x = {~a, b:2}    // means {a:a, b:2}
x = ~{a, b}      // means {a...