CreateSiteColumn.js

createsitecolumn: function () {
    
    var fieldschema = '<Field Type="' + sitecolumntype + '" Name="' + sitecolumnname + '" DisplayName="' + sitecolumndisplayname + '" Group="JSOM Provisioned Columns" />';
    var dfd = $.Deferred();

    var ctx = getContext();
    var appctx = getAppContextSite(ctx);

    var targetWeb = appctx.get_site().get_rootWeb();
    var fields = targetWeb.get_fields()
    fields.addFieldAsXml(fieldschema, false, SP.AddFieldOptions.addFieldCheckDisplayName);

    ctx.executeQueryAsync(function () { dfd.resolve(); }, function (sender, args) {
        console.log("Column creation failure: " + args.get_message());
        dfd.reject();
    });
    
    return dfd.promise();
}