Time and data
Another area that's difficult for React newcomers to grasp is the idea that JSX is like a static string, representing a chunk of rendered output. Are we just supposed to keep rendering this same view? This is where time and data come into play. React components rely on data being passed into them. This data represents the dynamic aspects of the UI. For example, a UI element that's rendered based on a Boolean value could change the next time the component is rendered. Here's an illustration of the idea:
Each time the React component is rendered, it's like taking a snapshot of the JSX at that exact moment in time. As our application moves forward through time, we have an ordered collection of rendered user interface components. In addition to declaratively describing what a UI should be, re-rendering the same JSX content makes things much easier for developers. The challenge is making sure that React can handle the performance demands of this approach.
