Concealed.js

<head>
  ...
  <script src="concealed.js"></script>
</head>
<body>
  ...
  <h1 data-conceal="3"></h1>
  <div class="summary" data-conceal="15"></div>
  ...
  <script>
    Conceal()
  </script>
</body>

import conceal from "concealed";
import React from "react";
import ReactDOM from "react-dom";

const App = () => (
  <div>
    <div className="content">
      <h1 data-conceal="2" />
    </div>
    <div className="content">
      <h2 data-conceal="4" />
      <div className="summary" data-conceal="50" />
    </div>
    <div className="content">
      <h2 data-conceal="3" />
      <div className="summary" data-conceal="30" />
    </div>
    <div className="content">
      <h2 data-conceal="2" />
      <div className="summary" data-conceal="20" />
    </div>
  </div>
);

ReactDOM.render(<App />, document.body);

conceal();