React was introduced in the last chapter, along with some simple examples. React will perform all of DOM manipulation and DOM event listening.
We will do a quick review of the life cycle events we are going to utilize in various components. The first is
componentWillMount. This is fired right before the component is rendered to the DOM. Next is
componentWillUnmount. Use this to clean up all the objects we initialized earlier. These first two functions we covered will only fire once in the life cycle. The
componentDidUpdate function is executed after the component renders any changes. This can be executed multiple times.