useEffect is a hook that allows us to perform side effects in function components. It combines componentDidMount, componentDidUpdate, and componentWillUnmount - by imamdev_ frontend javascript
in a single API. It's a compelling hook that will enable us to do many things. But it's also a very dangerous hook that can cause a lot of bugs.import React, { useEffect } from 'react' const Counter==> { const [count, setCount]=useState useEffect=> { const interval=setInterval=> { setCount=> c + 1) }, 1000) return => clearInterval }, []) return {count} }
It's a simple counter that increases every second. It uses useEffect to set an interval. It also uses useEffect to clear the interval when the component unmounts. The code snippet above is a widespread use case for useEffect.The problem with this example is that the interval is set every time the component re-renders. If the component re-renders for any reason, the interval will be set again. The interval will be called twice per second.
import React, { useEffect, useRef } from 'react' const Counter==> { const [count, setCount]=useState const intervalRef=useRef useEffect=> { intervalRef.current=setInterval=> { setCount=> c + 1) }, 1000) return => clearInterval }, []) return {count} } The above code is a lot better than the previous example. It doesn't set the interval every time the component re-renders. But it still needs improvement. It's still a bit complicated. And it still uses useEffect, which is a very dangerous hook.As we know about useEffect, it combines componentDidMount, componentDidUpdate, and componentWillUnmount in a single API.
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