In practice, the only thing that makes web experiences good is caring about the user experience — specifically, the experience of folks at the margins. Technologies come and go, but what always makes the difference is giving a toss about the user.

React dot JS, or simply “reaked”, is a not inconsiderable amount of JavaScript, written by some self-styled engineers, to help a website called Facebook undermine democracy, foment genocide, and do whatever else is needed to sell virtual advertising space…

React is useful for making complex interfaces like Facebook’s or for making otherwise simple interfaces, and their underlying codebases, complex like Facebook’s. Rendering the text “hello world” without React requires one text editor and exactly 11 bytes of code. Doing the same with React, via the popular “create-react-app” command line interface, requires over 200MB of Node modules. The continual maintenance and expert calibration needed to run a React application has created a thriving job market.

The React model describes an application as a tree of “components”. Each component represents a subset of the complete UI element tree. For each component, there is a template function that takes some inputs and returns the new desired state of the UI. This function is called whenever an event occurs that might change the state of the UI. The template produces a data structure known as a “virtual DOM”. To realize this new state in the actual DOM, React diffs the previous tree with the new one and updates, creates, and deletes elements as necessary.With FRP, you describe your program as an acyclic graph of nodes that contain time-varying values. The actual value of any given node is determined by a function that maps the current values of some input nodes into an output value. The system is bootstrapped by handling a UI event and updating the appropriate root node, which kicks off a cascade of updates throughout the graph.

Everything we’ve discussed today has mostly catered to the screen reader user experience. And while addressing issues for screen readers does help to remove barriers for other assistive technologies, such as keyboard-only and voice dictations users, it shouldn’t be the only focus.