Manual DOM manipulation is messy and keeping track of the previous DOM state is hard. A solution to this problem is to write your code as if you were recreating the entire DOM whenever state changes. Of course, if you actually recreated the entire DOM every time your application state changed, your app would be very slow and your input fields would lose focus. virtual-dom is a collection of modules designed to provide a declarative way of representing the DOM for your app. So instead of updating the DOM when your application state changes, you simply create a virtual tree or VTree, which looks like the DOM state that you want. virtual-dom will then figure out how to make the DOM look like this efficiently without recreating all of the DOM nodes.