I don\'t know much about WEB probramming, so feel free to ask if I\'m missing any details.
There is a certain website which I\'m visiting very frequently, and it require
The usual way to submit a form in general is to call submit() on the form itself, as described in krtek's answer.
However, if you need to actually click a submit button for some reason (your code depends on the submit button's name/value being posted or something), you can click on the submit button itself like this:
document.getElementById('loginSubmit').click();