index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="https://unpkg.com/axios@0.20.0/dist/axios.min.js"></script>
  </head>
  <body>
    <h1>static file server</h1>
    <input type="file" name="file" id="file" />
    <script>
      const file = document.getElementById('file');
      file.onchange = function (event) {
        const files = event.target.files;
        const file = files[0];
        const data = new FormData();
        data.append('file', file);
        axios.post('/upload', data).then((res) => {
          const image = new Image();
          image.src = res.data;
          image.onload = function () {
            document.body.append(image);
          };
        });
      };
    </script>
  </body>
</html>