Robert Scheitlin, GISP wrote:
React is what experience builder is built on.
That's very opinionated. If you're going to give an opinion on JavaScript frameworks you need to compare them all.
The choice of JavaScript all depends on the project requirements but make sure to note that if you start creating applications with one framework, it is a large amount of work to convert to another. The choice of framework all depends on your project requirements. There are three big JavaScript frameworks today, React, Angular, and Vue. All of them help speed up development of web applications in their own unique ways but you also don't have to use any JavaScript framework. The ArcGIS JavaScript API is built on top of Dojo, but I wouldn't recommend using it as it is quite outdated.
I've created a sample web application with all 3 frameworks to test the waters and this is what I found:
React: Generally OK to develop with. It's quick to learn but has its downfalls with data manipulation. If you need a significant number of form controls and inputs (ie. if you are using JS for data-manipulation applications) then React is not the way to go. React requires onChange events for every input control to update the state of the controller which loses a huge amount of time if you have a lot of data inputs. But overall, not a bad choice if you want to get started, just be weary that passing variables around can be a bit tricky.
Angular: Meh. It uses TypeScript which is a huge learning curve for anyone just getting into JavaScript. Being locked into using TypeScript with Angular can be beneficial because it enforces types for variables and requires compiling the JavaScript to build it but without knowing TypeScript there is a huge learning curve.
Vue: Fairly good. All around pretty decent to use. It is a sort of combincation of React and Angular but doesn't enforce typescript. It has automatic data-binding and JS objects get updated the moment a form input is changed. It's not too hard to get started and works well with Esri applications. Some downfalls with nested components and passing parameters but I've found it is nice to work with.
In addition to choice of framework, you should probably know the following concepts: ES6+, Webpack, Node.js, npm
Update: Was unaware Experience Builder was an Esri app. This app uses React, thus if you need any custom features it is required to be familiar with React. React is best built with JSX but there is really nothing to learn with JSX, it is just a file type that allows specifying HTML components directly in your JavaScript instead of requiring strings to create HTML elements. ES6+ is recommended as it has greatly improved JavaScript, but in general, you'll just need to be familiar with React states and their component lifecycle. I'd recommend walking through the React tutorial to get a grasp of things.
