Book Image

Learn Chart.js

By : Helder da Rocha
Book Image

Learn Chart.js

By: Helder da Rocha

Overview of this book

Chart.js is a free, open-source data visualization library, maintained by an active community of developers in GitHub, where it rates as the second most popular data visualization library. If you want to quickly create responsive Web-based data visualizations for the Web, Chart.js is a great choice. This book guides the reader through dozens of practical examples, complete with code you can run and modify as you wish. It is a practical hands-on introduction to Chart.js. If you have basic knowledge of HTML, CSS and JavaScript you can learn to create beautiful interactive Web Canvas-based visualizations for your data using Chart.js. This book will help you set up Chart.js in a Web page and show how to create each one of the eight Chart.js chart types. You will also learn how to configure most properties that override Chart’s default styles and behaviors. Practical applications of Chart.js are exemplified using real data files obtained from public data portals. You will learn how to load, parse, filter and select the data you wish to display from those files. You will also learn how to create visualizations that reveal patterns in the data. This book is based on Chart.js version 2.7.3 and ES2015 JavaScript. By the end of the book, you will be able to create beautiful, efficient and interactive data visualizations for the Web using Chart.js.
Table of Contents (14 chapters)
Title Page
Copyright and Credits
About Packt

Creating plugins

Plugins are the most efficient way to extend Chart.js. A plugin can insert code before and after different phases of the rendering cycle of a chart. At each phase, it can access the chart object and read configurable options. This can be used to change practically any property or behavior of the chart.

Plugins are designed to be reusable. During the previous chapters, we used several popular plugins to extend Chart.js in different ways. They are great to encapsulate complexity, but simple plugins can also be very useful.

In the last example, we created a download link for a PNG version of the chart. If you tried it, you may have noticed that the image has a transparent background. This is OK if your background is white, but if it isn’t, the chart may be hard to read. A naïve approach to fixing the problem would be painting the canvas white using CSS or fill commands. But, it won’t work because Chart.js redraws the canvas during its render cycle. You also need to deal with...