app.html

<h5>Start Ad-Placer!</h5>
<input type="submit" value="POST" onclick="submitPOST('query_param')" />
<input type="submit" value="GET" onclick="submitGET()" />

<script type="text/javascript">
  function submitPOST(name) {
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function () {
      if (xhr.readyState === 4) {
        //alert(xhr.response);
        console.log(xhr.response);
      }
    };
    xhr.open("post", "http://127.0.0.1:5000/post/" + name, true);
    xhr.setRequestHeader("Content-Type", "application/json");
    xhr.send(JSON.stringify('{"data":"body is here"}'));
  }
  function submitGET() {
    var xhr = new XMLHttpRequest();
    xhr.onreadystatechange = function () {
      if (xhr.readyState === 4) {
        //alert(xhr.response);
        console.log(xhr.response);
      }
    };
    xhr.open("get", "http://127.0.0.1:5000/get", true);
    xhr.send();
  }
</script>