Explain why componentDidMount is a better place to make an ajax request

In the docs, in componentWillMount section section it says:

Avoid introducing any side-effects or subscriptions in this method

And in the componentDidMount section:

If you need to load data from a remote endpoint, this is a good place to instantiate the network request

Which for me is confusing because I won't like to wait for the component to be mounted to dispatch an ajax call to fulfill the component data dependencies. I would like to do it as soon as possible, like in the constructor, not even in componentWillMount.

Clearly you may have a reason why you say this in the docs, I might be not seeing the bigger picture. So it will be nice if you can explain a bit more in detail or point me in the direction of where I can find the reason.

Lisez les sections liées sur componentWillMount et componentDidMount dans la documentation de React, ainsi que les indications environnantes sur le cycle de vie. Clarifiez pourquoi la documentation recommande de démarrer les requêtes distantes dans componentDidMount et répondez à la question de l’attente jusqu’au montage ; l’issue est terminée lorsque les indications de timing et leur justification sont claires.