Most front end frameworks these days are built around the concept of "reactivity" (not exclusive to React). This means that you describe the content of your UI in a declarative way, rather than imperative, as you would with plain JavaScript or something like jQuery.

For example, say you have a counter app, where clicking a button increases the count. With a traditional imperative coding style, clicking the button would trigger code to increment a variable, then update the value of the counter text with that variable. On the other hand, in a declarative style, clicking the button would trigger code only to increment the variable. Your framework would automatically detect that the value changed and update the counter text accordingly.

This makes your life much easier. You no longer have to worry about keeping the DOM in sync with your application state. Your framework does it for you.

Most web applications these days use a declarative framework, like Angular 2, React, or Vue.js. At BaseDash we use React — it's got a big community with wide support and lots of useful libraries. I've heard good things about Vue too.