how to hide a multi select lookup column based on a drop down value

Question

With the following code I am able to hide a normal lookup column based on drop down, But multi select I am not being able to

In multi select the identifier is SelectCanditate;SelectResult

Should I provide it together or as two separate variable.

function hideWorkgroupControl() {
        var control = getTagFromIdentifierAndTitle("select", "SelectCandidate", "Workgroup");

      //  var control = getTagFromIdentifierAndTitle("select", "SelectResult", "Personnel");
           control.parentNode.parentNode.parentNode.style.display = "none";

        //add an onchange event to the dropdown
        getTagFromIdentifierAndTitle("select", "DropDownChoice", "Types").onchange = function () { ChangeEvent() };


    }


    function ChangeEvent() {

        //get the dropdown
        var dropDown = getTagFromIdentifierAndTitle("select", "DropDownChoice", "Types");

        //get the selected value
        var option = dropDown.options[dropDown.selectedIndex].text;

        //get the control
        var control = getTagFromIdentifierAndTitle("select", "SelectCandidate", "Workgroup");

        //show hide based  on your condition
        if (option == "Workgroup") {
            control.parentNode.parentNode.parentNode.style.display = "";
        }
        else {
            control.parentNode.parentNode.parentNode.style.display = "none";
        }

    } 

    //this gets the field based on title identifier and tagname
    function getTagFromIdentifierAndTitle(tagName, identifier, title) {
        var len = identifier.length;
        var tags = document.getElementsByTagName(tagName);
        for (var i = 0; i < tags.length; i++) {
            var tempString = tags[i].id;
            if (tags[i].title == title && (identifier == "" || tempString.indexOf(identifier) == tempString.length - len)) {
                return tags[i];
            }
        }
        return null;
    }

Answer 1

function updateDropDownsforTask() {
    var dropdown = $("select[Title='Types']");
    if (dropdown.length != 0) {
        //$("select[Title='Workgroup']").parent().parent().parent().parent().hide();
        $("select[title='Workgroup selected values']").parent().parent().parent().hide();
        //$("input[Title='ReroutedUser']").parent().parent().parent().parent().hide();
        var dropdownid = dropdown[0].id;

        $('#' + dropdownid).change(function () {
            onChangeDropDown(dropdownid);
        });
    }
}

function onChangeDropDown(dropdownid) {
    var currentvalue = $('#' + dropdownid + ' :selected').text();
    var userdropdown = $("select[title='Workgroup selected values']");
    if (userdropdown.length == 0) {
        userdropdown = $("input[Title='Workgroup']");

        if (currentvalue == 'Workgroup') {
            userdropdown.parent().parent().parent().parent().show();
        }
        else {
            userdropdown.parent().parent().parent().parent().hide();
        }
    }
    else {

   if (currentvalue == 'Workgroup') {
       userdropdown.parent().parent().parent().show();

       //$("select[Title='ReroutedUser']").parent().parent().parent().show();
   }
   else {
       userdropdown.parent().parent().parent().hide();
   }

}

}