JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html><html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width" />
  <title>um</title>
  <link rel="stylesheet" href="style.css" />
</head>
<body>
  <div id="test"></div>

  <script src="script.js"></script>
</body>
</html>

JavaScript

var data = '{"employees":[{"firstName":"John0"},{"firstName":"Anna0"},{"firstName":"Peter0"}],"employees":[{"firstName":"John1"},  {"firstName":"Anna1"},{"firstName":"Peter1"}]};';

var json = JSON.parse(data);

document.querySelector('#test').innerHTML = json.employees[0].firstName;