I have a simple form for uploading a file. If I use an ordinary submit button, everything works as expected:
<form id="mainform" method="post" action="/" enctype="multipart/form-data">
...
<input type="submit" id="submit" value="Analyze File"/>
</form>
But if I change it to an ordinary button and use Javascript to submit the form, nothing happens:
<input type="button" id="submit" value="Analyze File" onclick="document.getElementById('mainform').submit()"/>
I verified that the onclick handler really is getting called, and looking up the form works correctly. For example, if I change it to onclick="alert(document.getElementById('mainform').action)", the alert comes up as expected and shows the target URL of the form. But for some reason, the call to submit() simply doesn't submit the form.