FormData doesn't iterate over disabled inputs

If I have a form that looks like this:

<form>
  <input disabled name="first_name" />
  <input name="last_name" />
</form>

And then I use FormData to iterate over the inputs.

const form = new FormData(formElement);

const fieldNames = [];

form.forEach((value, name) => {
  fieldNames.push(name);
});

// fieldNames contains ['last_name']

Then fieldNames only contains one name!

Be careful if you're using FormData to extract names from a form!