Get the documentURI with JS

JS

function run_function() {
  var documentURI = document.documentURI;
  write_result(documentURI);
  return documentURI;
}

// this is a common function just to write the content into the result div
function write_result(result) {
  var result_html = document.getElementById("result");
  result_html.innerHTML = result;
}

HTML

<div id='result' class='mb-3 alert alert-primary'>..</div>
<button onclick='run_function();' class='btn btn-primary mb-1'>Run Function</button>

Working Result

Test Result Below