tauri-plugins-workspace/plugins/single-instance/examples/emit-event/public/index.html

<html>
  <body>
    <div>Plugin example</div>
    <pre id="args"></pre>
    <script type="module">
      var argsEl = document.getElementById("args");

      function cliProtocolVal({
        args: {
          color: { value },
        },
      }) {
        argsEl.innerHTML = value;
        document.body.style.backgroundColor = value;
      }
      function cliProtocolErr(err) {
        argsEl.innerHTML = JSON.stringify(err);
      }

      window.__TAURI__.cli
        .getMatches()
        .then(cliProtocolVal)
        .catch(cliProtocolErr);

      await window.__TAURI__.event.listen(
        "single-instance",
        ({ event, ...eventObj }) => {
          console.log(event, eventObj);
          let args = eventObj.payload?.args;

          if (args?.length > 1) {
            let color = args[1];
            argsEl.innerHTML = color;
            document.body.style.backgroundColor = color;
          }
        }
      );
    </script>
  </body>
</html>