Why componentWillMount should not be used?

Question

Firing server call to fetch data in componentWillMount life cycle method a bad practice?

And why it is better to use componentDidMount.

Answer 1

UPDATE: componentWillMount will soon be deprecated.

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To cite @Dan Abramov

In future versions of React we expect that componentWillMount will fire more than once in some cases, so you should use componentDidMount for network requests.

Read more here.