db/DB.js: allow a Promise return instead of callbacks in init()

src/node/db/DB.js

@@ -35,7 +35,7 @@ exports.db = null;
  * Initalizes the database with the settings provided by the settings module
  * @param {Function} callback
  */
-exports.init = function(callback) {
+function init(callback) {
   // initalize the database async
   db.init(function(err) {
     if (err) {
@@ -50,3 +50,19 @@ exports.init = function(callback) {
     }
   });
 }
+
+/**
+ * Initalizes the database with the settings provided by the settings module
+ * If the callback is not supplied a Promise is returned instead.
+ * @param {Function} callback
+ */
+exports.init = function(callback)
+{
+  if (callback === undefined) {
+    return new Promise(resolve => init(resolve));
+  } else if (typeof callback === "function") {
+    init(callback);
+  } else {
+    throw new TypeError("DB.init callback parameter");
+  }
+}