I have a form field (a series of checkboxes) that's being created dynamically from a database, so it's possible that the field will not exist on the form (if there are no matching values in the database). I have some code that needs to execute based on whether the field exists, and pull in the values that are selected if it does exist. I can't seem to get javascript to acknowledge that this field exists, though. Here's what I've tried:

function displayAction(){

    var f = document.adminForm;

    var a = f.action;



    if(f.prefix.value!=-) {

        a = a + '&task=callExclusionDisplay&prefix=' + f.prefix.value;

    }

    else {

        var exclusions = document.getElementById(exclusions);

        if (exclusions != null){

            alert(exclusions set);

            a = a + '&task=callExclusionCreate&prefix=' + f.prefix.value + '&exclusions=' + exclusions.join();

        }

    }

    alert('after if, action is ' + a);

}

The code never passes the if statement checking to see if exclusions is not null, even though when I look at the page there are a number of checkboxes named exclusions (with the id also set to exclusions). Is the issue with !=null because it's a group of checkboxes, rather than a single form element? How can I get this to work? If I skip the test for null, the code throws errors about exclusions not being defined if the database doesn't return any matching values.