JSOM code that will populate a dropdown box with field values from a SharePoint List.

dashboard.js

<script type="text/javascript">

var updateQueryString = null;

$(document).ready(function() {

    // customize these variables
    var _dropDownId               = "applicationNames";       // this must match the ID of the select element placed on the wiki page (<select id="applicationNames">></select>)
    var _listTitle                = "Applications";           // title of the list that stores the items to display in the list
    var _displayFieldInternalName = "App_x0020_Name"; // this the internal name of the field that stores the values to display in the dropdown
    var _valueFieldInternalName   = "lookup";         // this the internal name of the field that stores the values to display in the dropdown
    var _queryStringKey           = "application";            // query string key value, this must match the web part filter config


    // should not have to change anything below this point
    var _listItems         = null;  
    var _select            = $('<select>');

    SP.SOD.executeFunc('sp.js', 'SP.ClientContext', onSharePointReady);

    function populateApplicationList(sender, args) 
    {  
        var listItem;
        var enumerator = _listItems.getEnumerator();  
        var valueField;
        var displayField;

        // clear all options
        $("#" + _dropDownId).empty()

        // add default option
        // $("<option value=''>Select an Application</option>").appendTo("#" + _dropDownId)

        // add each application
        while ( enumerator.moveNext() ) 
        {  
            listItem     = enumerator.get_current();
            displayField = listItem.get_item(_displayFieldInternalName).get_description(); // use the description form the URL field
            valueField   = listItem.get_item(_valueFieldInternalName);  // this field value could be null

            if( valueField != null)
            {
                // pull the value from the lookup field
                valueField = valueField.get_lookupValue();
            }
            else
            {
                // sometimes the lookup field is empty, so fall back to display field value
                valueField = displayField;
            }

            $("<option value='" + valueField + "'>"+ displayField + "</option>").appendTo("#" + _dropDownId)
        }
    }  

    function logErrorMessage(sender, args) 
    {
        console.error("EXCEPTION QUERYING LIST ITEMS: " + args.get_message());
    } 

    function onSharePointReady()
    {
        var context = SP.ClientContext.get_current();
        var listId  = _spPageContextInfo.pageListId;
        var list    = context.get_web().get_lists().getByTitle(_listTitle);

        var caml = new SP.CamlQuery();
        caml.set_viewXml("<View><Query><OrderBy><FieldRef Name='" + _displayFieldInternalName + "' Ascending='True' /></OrderBy></Query><ViewFields><FieldRef Name='" + _displayFieldInternalName + "' /><FieldRef Name='" + _valueFieldInternalName + "' /></ViewFields><QueryOptions /></View>");     

        _listItems = list.getItems(caml); 
        context.load(_listItems);  
        
        context.executeQueryAsync(populateApplicationList, logErrorMessage);  
    }

    updateQueryString = function (){   
        
        var queryStringValuePairs = {};

        if( $( "#" + _dropDownId + " option:selected" ).index() > 0)
        {
            $.each(document.location.search.substr(1).split('&'),function(c,q){
                var i = q.split('=');

                if( i[0].length > 0)
                {
                    queryStringValuePairs[i[0].toString()] = i[1].toString();
                }
            });

            queryStringValuePairs[_queryStringKey] =  $( "#" + _dropDownId + " option:selected" ).val().toLowerCase();
    
            var newUrl = document.location.href.split('?')[0]
            newUrl = newUrl + "?" + $.param(queryStringValuePairs)
            window.location.href = newUrl;
        }
    }

    // add onChange event to drop down, SharePoint may strip out the javascript  
    $( "#" + _dropDownId ).on( "change", function () {
        updateQueryString();
    });
});

</script>