title: FormData based on form id or name
body: <p>I have a button outside of form data. When i submit the form, i can get the serialize value but not <code>FormData</code>. How can i get the FormData?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>function submitForm() {
    console.log($('#form1').serialize());
    console.log(new FormData(document.getElementById('form1')));
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;form id="form1" name="form1"&gt;
      &lt;input type="firstname" value="First Name" name="firstname"&gt;
      &lt;input type="lastname" value="Last Name" name="lastname"&gt;
  &lt;/form&gt;
  &lt;button onclick="submitForm()"&gt;Submit&lt;/button&gt;</code></pre>
  </div>
  </div>
  </p>