useEffect Hook in react

app.js

import React,{useState, useEffect} from 'react';
import Note from './components/Note'
import axios from 'axios'

const App = () => {
  const [notes,setNotes] = useState([])
  const [newNote,setNewNote] = useState('')
  const [showAll,setShowAll] = useState(true)

  const hook = ()=> {
    console.log("effect")
    axios.get("http://localhost:3001/notes")
    .then(response => {
      console.group("promise fulfilled")
      setNotes(response.data)
    })
  
  }

useEffect(hook,[])
console.log('render',notes.length,'notes')

return (
  <h1>Hello World!</h1>
)

}
export default App;