index.js in index.html code example
Example: default index.html code reac
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
<title>React App</title>
</head>
<body>
<div id="root"></div>
</body>
</html>