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
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Pattern matching


Pattern matching is a generalization of C language or Java's switch statement. In C language and Java, the switch statement only allows you to choose from many statements based on an integer (including char) or an enum value. While in Opa, pattern matching is more powerful than that. The more general syntax for pattern matching is:

match(<expr>){
case <case_1>: <expression_1>
case <case_2>: <expression_2>
case <case_n>: < expression_n>
}

When a pattern is executed, <expr> is evaluated to a value, which is then matched against each pattern in order until a case is found. You can think about it this way:

if (case_1 matched) expression_1 else {
  if (case_2 matched) expression_2 else {
    ...
         if (case_n matched) expression_n else no_matches
         ...
  }
}

The rules of pattern matching are simple and are as follows:

  • Rule 1: Any value matches the pattern _

  • Rule 2: Any value matches the variable pattern x, and the value...