React hooks - useEffect fundamentals
What is an effect?
A side-effect, in short an “effect”, is anything that a function tries to modify outside of its body. It’s not a direct result of its arguments and return value.
In React, most of the effects happen after the DOM is updated (
render ). In class components, these are covered by
componentDidMount for the initial render, and
componentDidUpdate for each updates, and
componentWillUnmount when the component is disposed.
Usual effects include:
- data fetching
- subscription to external data sources
- imperative updates to DOM
- any sort of cleanup in
When using the new Hooks, each effect function goes into the