what is useeffect and signal hook react code example

Example 1: componentdidmount hooks

For componentDidMount
useEffect(() => {
  // Your code here
}, []);

For componentDidUpdate
useEffect(() => {
  // Your code here
}, [yourDependency]);

For componentWillUnmount
useEffect(() => {
  // componentWillUnmount
  return () => {
     // Your code here
  }
}, [yourDependency]);

Example 2: react useeffect

import React, { useEffect } from 'react';
	
	const [data,setData]=useState()
    useEffect(() => {
        fetch(`put your url/api request in here`)
        .then(res=>res.json())
        .then(json => setData(json))
    },[])