www.pdelong.com

 1const form = document.getElementById("form");
 2const input = document.getElementById("input");
 3const output = document.getElementById("output");
 4const errors = document.getElementById("error");
 5
 6form.addEventListener("submit", (event) => {
 7  event.preventDefault();
 8
 9  try {
10    if (event.submitter.id == "encode") {
11      output.value = btoa(input.value);
12    } else if (event.submitter.id == "decode") {
13      output.value = atob(input.value);
14    }
15  } catch (e) {
16    while (errors.firstChild) {
17      errors.removeChild(errors.firstChild);
18    }
19
20    var error = document.createElement("p");
21    error.classList.add("warning");
22    error.append(e.message);
23    errors.append(error);
24  }
25
26  return false;
27});