The next lifecycle method you're going to learn about is used to implement heuristics that improve component rendering performance. You'll see that if the state of a component hasn't changed, then there's no need to render. Then, you'll implement a component that uses specific metadata from the API to determine whether or not the component needs to be re-rendered.
The shouldComponentUpdate() lifecycle method is used to determine whether or not the component will render itself when asked to. For example, if this method were implemented, and returned false, the entire lifecycle of the component is short-circuited, and no render happens. This can be an important check to have in place if the component is rendering a lot of data and is re-rendered frequently. The trick is knowing whether or not the component state has changed.
This is the beauty of immutable data—we can easily check if it has changed. This is especially true if we're using...