[ReactJS] useEffect _영화 웹 서비스 만들기

import { useState, useEffect } from "react";

function App() {
  const [counter, setCounter] = useState(0);
  const [keyword, setKeyword] = useState("");
  const onClick = () => setCounter((prev) => prev + 1);
  const onChange = (event) => setKeyword(event.target.value);
  
  // console.log("i run all time.");
  
  useEffect(() => {
    console.log("i run only once.");
  }, []);
  
  useEffect(()=>{
    console.log("i run when 'keyword' changes.");
  }, [keyword]);

  useEffect(()=>{
    console.log("i run when 'counter' changes.");
  }, [counter]);

  useEffect(()=>{
    console.log("i run when 'keyword' & 'counter' changes.");
  }, [counter, keyword]);

  return (
    <div>
      <input type="text" placeholder="Search for..." onChange={onChange}/>
      <h3>{counter}</h3>
      <button onClick={onClick}>Click me</button>
    </div>
  )
}

export default App;