React

by Abdul Ahmad

HTML

<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

let intervalId;
let counterGlobal;
function initCounter({ setCounter }) {
  intervalId = setInterval(() => {
  	setCounter(counterGlobal + 1);
  }, 1000);
} 

function App() {
  const [counter, setCounter] = React.useState(0);
  counterGlobal = counter;
  
	React.useEffect(() => {
    initCounter({ setCounter});
  }, []);

	return (
  	<div>
      counter: { counter }
      <Comp1 />
      <Comp2 />
    </div>
  );
}

function Comp1({ x = {} }) {
	console.log('rendering comp 1');
  return 'comp 1';
}

const defValY = {};
function Comp2({ y = defValY }) {
	console.log('rendering comp 2');
  return 'comp 2';
}


ReactDOM.render(<App />, document.querySelector("#app"))