If you place inside form input or selectbox with name "action" then code $('#form-id').attr('action', 'new-action'); will work with this element. Not with form attribute.

But $('#form-id').attr('action') will return real form action.

Examples of HTML:

<form action="test-action" id="form-id">

<select name="action">

<option value="1">Option 1</option>

</select>

</form>

<form action="test-action" id="form-id">

<input name="action" type="text">

</form>