How to use JavaScript to change the form action [duplicate]

function chgAction( action_name )
{
    if( action_name=="aaa" ) {
        document.search-theme-form.action = "/AAA";
    }
    else if( action_name=="bbb" ) {
        document.search-theme-form.action = "/BBB";
    }
    else if( action_name=="ccc" ) {
        document.search-theme-form.action = "/CCC";
    }
}

And your form needs to have name in this case:

<form action="/"  accept-charset="UTF-8" method="post" name="search-theme-form" id="search-theme-form">

Try this:

var frm = document.getElementById('search-theme-form') || null;
if(frm) {
   frm.action = 'whatever_you_need.ext' 
}

If you're using jQuery, it's as simple as this:

$('form').attr('action', 'myNewActionTarget.html');