I have an typo3 form (action="update") which should be sended via jquery.
Form looks like this:
<f:form action="update" name="note" object="{note}">
<textarea class="form-control gettooltip" rows="1" placeholder="Kommentar" title="Kommentar zur Note">{note.kommentar}</textarea>
</f:form>
Just to warn you to not follow our team way, when you try to use some custom AJAX dispatcher, then switch to different pageType, after that to eID or whatever. My recommended way to do AJAX calls within TYPO3 is to use EXT:typoscript_rendering
Find this article from extension's author, which has links to root causes and usage example.
And a Github repository.