코드네임 :

import { useState, useEffect } from "react";function App() { const [loading, setLoading] = useState(true); const [coins, setCoins] = useState([]); useEffect(() => { fetch("https://api.coinpaprika.com/v1/tickers") .then((response) => response.json()) .then((json) => { setCoins(json); setLoading(false); }); }, []); return ( div> h1>The Coins! {loading ? "" : `(${coins.length})`}h1> {loading ? stro..

import { useState, useEffect } from "react";function App() { const [toDo, setToDo] = useState(""); const [toDos, setToDos] = useState([]); const onChange = (event) => setToDo(event.target.value); const onSubmit = (event) => { event.preventDefault(); if (toDo === "") { return; } // 중요!!!! state를 절대 직접 수정하지 않고, 함수로 수정 // 그러니 toDo ="";는 절대 안되고 아래처럼 setToDos((currentArray) => [toDo, ...currentArray]..

그뭐니 nodejs로 지금 뭐 실행중이던데 index.jsimport React from "react";import ReactDOM from "react-dom/client";import App from "./App";const root = ReactDOM.createRoot(document.getElementById('root'));root.render( React.StrictMode> App /> React.StrictMode>);   App.jsimport { useState, useEffect } from "react";function App() { const [counter, setValue] = useState(0); const [keyword, setKeyword] = useState("")..

흠 중간에 ?? 한 부분있어서 지피티한테 무러봣긔바로 이해함 굿   DOCTYPE html>html lang="en"> head> meta charset="UTF-8" /> meta name="viewport" content="width=device-width, initial-scale=1.0" /> title>Documenttitle> head> body> div id="root">div> body> script src="https://unpkg.com/react@17.0.2/umd/react.development.js">script>  script src="https://unpkg.com/react@17.0.2/umd/react.development.js">script> script src="http..

DOCTYPE html>html lang="en"> head> meta charset="UTF-8" /> meta name="viewport" content="width=device-width, initial-scale=1.0" /> title>Documenttitle> head> body> div id="root">div> body> script src="https://unpkg.com/react@17.0.2/umd/react.production.min.js">script> script src="https://unpkg.com/react-dom@17.0.2/umd/react-dom.production.min.js">script> script src="https://unpkg.com/@babel/stan..

html 태그는 소문자로컴포넌트는 대문자로 흠 리액트는 코드 재사용이 쉬워보이는 군요  const [변수, 변수_변경함수] = React.useState(초기값);  DOCTYPE html>html lang="en"> head> meta charset="UTF-8" /> meta name="viewport" content="width=device-width, initial-scale=1.0" /> title>Documenttitle> head> body> div id="root">div> body> script src="https://unpkg.com/react@17.0.2/umd/react.production.min.js">script> script src="https://unpkg.com/react-..

JS에서는 HTML을 먼저 만들고 그걸 javascript로 가져와서 수정하는 식이었으나ReactJS는 모든걸 javascript로 먼저 시작한다DOCTYPE html>html lang="en"> head> meta charset="UTF-8" /> meta name="viewport" content="width=device-width, initial-scale=1.0" /> title>Documenttitle> head> body> div id="root">div> body> script src="https://unpkg.com/react@17.0.2/umd/react.production.min.js">script> script src="https://unpkg.com/react-dom@17.0.2/u..