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

Component Mounting life cycle is

• constructor()
• componentWillMount() /UNSAFE_componentWillMount()(react 16)
• render()
• componentDidMount()

Constructor and componentWillMount both call before render() call which is responsible for page rendering.

Here State initialized is done in Constructor and api are called in componentDidMount because of async calls.

ComponentWillMount was good to initialized state before ES6 when constructor was not there. But now ComponentWillMount is good for nothing and react team is thinking it after react 17.

In addition to above, react have moved to react fiber architecture, to avoid unnecessary re-rendering and improve performance, react has decided to move away from componentWillMount, componentWillReciveProps and componentWillUpdate methods.