If I want some code to run on every render, should I put it in a useEffect or directly in a component and what's the difference between those approaches?
What are common pitfalls when using useEffect?
What are differences between mounting, rendering and updating the DOM? When is useEffect really called?
It is not guaranteed that useEffect function will be called on every rerender .
But in the following case it will :
If you pass some state in the dependency array , so whenever that state changes its value then it would mean two things to the react . changing this value will cause useEffect function to be called again , and also since this is a state , it will rerender the component .
Order of execution will be( after initial render ) :
1 . New component will be rendered and it will be displayed on to the browser (also called painted on to the browser )
2 . if you have defined some cleanup function , then cleanup function will be called for the previous component .
3 . At last useEffect function will be called for this new component .
There is this beautiful and comprehensive article on the same by Dan Abramov . overreacted.io/a-complete-guide-to...
Take a look for better understanding .
Happy coding
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What about a cleanup function?
If I want some code to run on every render, should I put it in a
useEffector directly in a component and what's the difference between those approaches?What are common pitfalls when using
useEffect?What are differences between mounting, rendering and updating the DOM? When is
useEffectreally called?for a cleanup function you would use return inside of it, might look like this
useEffect(()=>{
// Code
return () => {
//code
}
},[]);
here's an example from react docs
reactjs.org/docs/hooks-effect.html...
It is not guaranteed that useEffect function will be called on every rerender .
But in the following case it will :
If you pass some state in the dependency array , so whenever that state changes its value then it would mean two things to the react . changing this value will cause useEffect function to be called again , and also since this is a state , it will rerender the component .
Order of execution will be( after initial render ) :
1 . New component will be rendered and it will be displayed on to the browser (also called painted on to the browser )
2 . if you have defined some cleanup function , then cleanup function will be called for the previous component .
3 . At last useEffect function will be called for this new component .
There is this beautiful and comprehensive article on the same by Dan Abramov . overreacted.io/a-complete-guide-to...
Take a look for better understanding .
Happy coding