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.

Leggi le sezioni collegate su componentWillMount e componentDidMount nella documentazione di React, insieme alle indicazioni circostanti sul ciclo di vita. Chiarisci perché la documentazione raccomanda di avviare le richieste remote in componentDidMount e affronta la preoccupazione di dover aspettare il mount; l’issue è completata quando le indicazioni sui tempi e la motivazione sono chiare.