React

by Fulvio Cezar Canducci Dias

HTML

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<div id="app"></div>

CSS

body {
  background: #20262E;
  padding: 20px;
  font-family: Helvetica;
}

#app {
  background: #fff;
  border-radius: 4px;
  padding: 20px;
  transition: all 0.2s;
}

li {
  margin: 8px 0;
}

h2 {
  font-weight: bold;
  margin-bottom: 15px;
}

.done {
  color: rgba(0, 0, 0, 0.3);
  text-decoration: line-through;
}

input {
  margin-right: 5px;
}

React

const CountContext = React.createContext();
function CountProvider({children}) {
	const [count, setCount] = React.useState(0);
	return (
  	<CountContext.Provider 
      value={{count, setCount}}>
      {children}
    </CountContext.Provider>
  )
}
function useCount() {
	const {count, setCount} = React.useContext(CountContext);
  return [count, setCount];
}
function Increment() {
	const [count, setCount] = useCount();
  const handleIncCount = () => setCount(count + 1);
	return (
  	<div>
      <label>Segundo Componente</label>
  	  <div>{count}</div>
      <div style={{marginTop: 15}}>
        <button onClick={handleIncCount} className="btn btn-primary">
          Incrementar
        </button>
      </div>
    </div>
  )
}

function Count() {
	const [count] = useCount();
	return (
  	<div>
  	  <label>Primeiro Componente</label>
  	  <div>{count}</div>
    </div>
  )
}

function App() {
	return (
  	<CountProvider>
  	  <Count />
      <hr />
      <Increment />
  	</CountProvider>
  )
}
ReactDOM.render(<App />, document.querySelector("#app"))