Although fallbacks are useful when scripting is not available, you should still aim to make your scripted content accessible to all readers. Enter the W3C Web Accessibility Initiative’s (WAI) Accessible Rich Internet Application (ARIA) specification.
The technology defined in this specification can be used in many
situations to improve content accessibility. We’ve already encountered
aria-describedby attribute in
looking at how to add descriptions and summaries, for example.
I’m now going to pick out three common cases for scripting to further explore how ARIA can enhance the accessibility of EPUBs: custom controls, forms, and live regions.
Custom controls are not standard form elements that you stylize to suit your needs, just to be clear. Those are the good kinds of custom controls—if you want to call them custom—as they retain their inherent accessibility traits whatever you style them to look like. Readers will not have problems interacting with these controls as they natively map to the underlying accessibility APIs, and so will work regardless of the scripting capabilities any reading system has built in.
A custom control is the product of taking an HTML element and enhancing it with script to emulate a standard control, or building up a number of elements for the same purpose. Using images to simulate buttons is one of the more common examples, as custom toolbars are often created in this way. There is typically no native way for a reader ...