react native componentwillmount vs componentdidmount

1The best place to make calls to fetch data is within componentDidMount(). 
2componentDidMount() is only called once, on the client, compared to 
3componentWillMount() which is called twice, once to the server and 
4once on the client. It is called after the initial render when the 
5client received data from the server and before the data is displayed 
6in the browser.