test.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>UPL JS Test</title>
  </head>
  <body>
    <script type="text/javascript" src="./target/scala-2.13/upl-fastopt/main.js"></script>
    <script type="text/javascript">
    var prog = null
    function check() {
      var pS = document.getElementById("progIn").value
      prog = UPL.checkProgram(pS)
      document.getElementById("progOut").value = UPL.print(prog)
    }
    function eval() {
      var eS = document.getElementById("in").value
      var eI = UPL.runIn(prog, eS)
      document.getElementById("out").value = UPL.print(eI)
    }
    </script>

    <div>
      <textarea id="progIn">module M {x = 1}</textarea>
      <button onclick="check()">Check</button>
      <textarea id="progOut"></textarea>
    </div>
    <div>
      <textarea id="in">M.x</textarea>
      <button onclick="eval()">Evaluate</button>
      <textarea id="out"></textarea>
    </div> 
  </body>
</html>