Client-side applications, such as interactive Web graphics, depend on browser support. This book assumes that your audience uses browsers that support HTML5 Canvas and ES2015 (which include all modern browsers). All examples use ES2015 syntax, including const and let instead of var, arrow functions where appropriate, spread operators, maps, sets, and promises. External files are loaded using the Fetch API, which has only been supported more recently, but you can easily switch to JQuery if necessary.

Although the creation of visualizations with Chart.js is mostly a declarative process, it is still a JavaScript library and requires basic knowledge of JavaScript. To create a simple chart, you need to know how to declare constants and variables, perform basic mathematical Boolean string and attribution operations, call and create functions, manipulate objects and arrays, and instantiate the Chart.js object. A typical chart also requires enough knowledge to program control structures, write callbacks, sort and filter datasets, generate random numbers, and load external files. This section is a quick refresher on the main ES2015 topics you will need to use Chart.js.