Jumperless/JumperlessNano/Adafruit_TinyUSB_Arduino/docs/examples/webusb-rgb/application.js

(function() {
  'use strict';

  document.addEventListener('DOMContentLoaded', event => {
    let connectButton = document.querySelector("#connect");
    let statusDisplay = document.querySelector('#status');
    let port;

    function connect() {
      port.connect().then(() => {
        statusDisplay.textContent = '';
        connectButton.textContent = 'Disconnect';

        port.onReceiveError = error => {
          console.error(error);
        };
      }, error => {
        statusDisplay.textContent = error;
      });
    }

    connectButton.addEventListener('click', function() {
      if (port) {
        port.disconnect();
        connectButton.textContent = 'Connect';
        statusDisplay.textContent = '';
        port = null;
      } else {
        serial.requestPort().then(selectedPort => {
          port = selectedPort;
          connect();
        }).catch(error => {
          statusDisplay.textContent = error;
        });
      }
    });

    serial.getPorts().then(ports => {
      if (ports.length === 0) {
        statusDisplay.textContent = 'No device found.';
      } else {
        statusDisplay.textContent = 'Connecting...';
        port = ports[0];
        connect();
      }
    });

    let colorPicker = document.getElementById("color_picker");

    colorPicker.addEventListener("change", function(event) {
      port.send(new TextEncoder("utf-8").encode(colorPicker.value));
    });
  });
})();