You should move all the code from the componentWillMount to the constructor or componentDidMount.
componentWillMount() is invoked just before mounting occurs. It is called before render(), therefore calling setState() synchronously in this method will not trigger an extra rendering. Generally, we recommend using the constructor() instead.
Avoid introducing any side-effects or subscriptions in this method. For those use cases, use componentDidMount() instead.
This is the only lifecycle hook called on server rendering.componentDidMount() is invoked immediately after a component is mounted. Initialization that requires DOM nodes should go here. If you need to load data from a remote endpoint, this is a good place to instantiate the network request.
This method is a good place to set up any subscriptions. If you do that, don’t forget to unsubscribe in componentWillUnmount().
Calling setState() in this method will trigger an extra rendering, but it will happen before the browser updates the screen. This guarantees that even though the render() will be called twice in this case, the user won’t see the intermediate state. Use this pattern with caution because it often causes performance issues. It can, however, be necessary for cases like modals and tooltips when you need to measure a DOM node before rendering something that depends on its size or position.