javascript auto submit to form without name (tumblr)

[CageOnede]

I want to make auto submit code in JavaScript for Tumblr but the problem is that the form doesnt have name. I cant edit html I will put code in Tampermonkey in Chrome (same as Greasmonkey in Firefox).\[code\]<form id="post_form" style="" enctype="multipart/form-data" class="active" data-post-type="photo"><div>some photo</div><button class="chrome blue txt " type="submit">Reblog post</button></form>\[/code\]I tried a number of ways but nothing works.