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

Drawing a shape

Now that we have the context of our canvas element, we can draw graphics on it. Opa and JavaScript use similar code to draw the graphics. The primary difference between them is that the drawing functions in Opa are static. All drawing methods can be found in the Canvas module.

Using the fill and stroke properties

Whenever we wish to draw shapes on a canvas, there are two properties that we need to set: Stroke and Fill. Stroke and fill determine how the shape is drawn. The stroke property is used for the outline of a shape; the fill property is used for the inside of a shape. In the following example, the first two lines fill a rectangle, whereas the last three lines stroke a rectangle:

Following is the result of the preceding code fragment: