I'm trying to click on a submit button and submit a form using purely javascript. I have tried:

document.getElementById('sell_form').submit();

and

for(var i=0;i<document.getElementsByName('operation').length;i++){

    if(document.getElementsByName('operation')[i].value=='Sell'){

        document.getElementsByName('operation')[i].submit();

    }

}

but I just can't get it. Can anyone show me how I could do this?

Thanks in advance.

The web code is:

<form id=sell_form class=ajaxform action=/member/sell method=post>

    <div id=result class=popup> </div>  //hidden

    <div class=c-box-body>

        <table width=100% border=0>

        <div style=text-align:center>

            <br>

            <input type=hidden value=13 name=pair>    //hidden

            <input type=hidden value=Sell name=type>  //hidden

            <input type=submit value=Calculate name=calculate>

            <input type=submit value=Sell name=operation>   //**This is the one I'm trying to click on

            <input type=reset value=Clear>

        </div>

    </div>

</form>

What makes this difficult is that the web page is not mine (I'm using greasemonkey in firefox which is essentially and onload javascript event)