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

Text parsers

Parsing is something that web apps need to do quite often. Opa features a built-in syntax for building text parsers, which are first class values just as functions. The parser is based on parsing expression grammar (, which may look like regular expressions at first, but do not behave anything like them. One big advantage of text parsers over regular expressions is that you can easily combine parsers. A good example is parsing URLs. Let's start right away with our first Opa parser:

first_parser = parser { 
case "Opa"  : 1 

For first_parser, the expressions are just literal strings, which means this parser will succeed only if fed with the string "Opa". Then how to use this parser? The module Parser ( has a bunch of functions to deal with parsers. The most important one is:

Parser.try_parse : Parser.general_parser('a), string -> option('a)

It takes a parser and a string...