useeffect lifecycle code example
Example 1: useeffect with cleanup
useEffect(() => {
//your code goes here
return () => {
//your cleanup code codes here
};
},[]);
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))
},[])
Example 3: useeffect componentdidmount
import React, { useState, useEffect } from 'react';
function Example() {
const [count, setCount] = useState(0);
// Similar to componentDidMount and componentDidUpdate:
useEffect(() => {
// Update the document title using the browser API
document.title = `You clicked ${count} times`;
});
);
}
Example 4: componentwillunmount hooks
useEffect(() => {
window.addEventListener('mousemove', () => {});
// returned function will be called on component unmount
return () => {
window.removeEventListener('mousemove', () => {})
}
}, [])
Example 5: useeffect componentdidmount
useEffect(() => {
messagesRef.on('child added', snapshot => {
const message = snapshot.val();
message.key = snapshot.key;
setMessages(messages.concat(message)); // See Note 1
}, []); // See Note 2