According to the syntax of React.createClass, getDefaultProps() and getInitialState can be used but the syntax changes when we use React.Component.
prop-types npm package is used for validating Prop types. You have to first install it using:
npm install --save prop-types
Refer here in case of any issues related to prop-types
Mounting is the process that occurs when a component is being inserted into the DOM. This phase has two methods that we can hook up with: componentWillMount() and componentDidMount().
All the AJAX requests should be put-up inside componentDidMount() hook.
I am pretty much sure you would be thinking why? So here is the answer.
You can also refer this for more info.
For explaining the below line:
It’s very important to note that calling this.setState() within componentWillMount method will not trigger a re-render.
This is because, the render() method hasn't been called yet. Thus, its re-render is actually the first-time rendering of the render method. However, in case of componentDidMount() method, the render method has already been called and so this.setState re-renders it again.
It is called immediately before the component is unmounted from the DOM.
One last method that is worthy to note is forceUpdate(). As mentioned earlier, React will re-render components as props in use change (or componentWillReceiveProps is called). If there is a need to update the component while props are not changing, then forceUpdate can be called.
Refer here
forceUpdate should be avoided because it deviates from a React mindset. The React docs cite an example of when forceUpdate might be used:
By default, when your component's state or props change, your component will re-render. However, if these change implicitly (eg: data deep within an object changes without changing the object itself) or if your render() method depends on some other data, you can tell React that it needs to re-run render() by calling forceUpdate().