Initializing properties and state

In this section, you'll see how to implement initialization code in React components. This involves using lifecycle methods that are called when the component is first created. First, we'll walk through a basic example that sets the component up with data from the API. Then, you'll see how state can be initialized from properties, and also how state can be updated as properties change.

Fetching component data

One of the first things you'll want to do when your components are initialized is populate their state or properties. Otherwise, the component won't have anything to render other than its skeleton markup. For instance, let's say you want to render the following user list component:

import React from 'react'; 
import { Map as ImmutableMap } from 'immutable'; 
 
// This component displays the passed-in "error" 
// property as bold text. If it's null, then 
// nothing is rendered. 
const ErrorMessage = ({ error }) => 
...