Refactor promise usage and return it only if no callback provided

lib/multi_caching.js

@@ -53,7 +53,11 @@ var multiCaching = function(caches, options) {
             options = {};
         }
 
-        var defer = Promise.defer();
+        var promised = false;
+        if (!cb) {
+            cb = Promise.defer();
+            promised = true;
+        }
 
         var i = 0;
         async.eachSeries(caches, function(cache, next) {
@@ -66,10 +70,10 @@ var multiCaching = function(caches, options) {
 
                 if (_isCacheableValue(result)) {
                     // break out of async loop.
-                    if (typeof cb === 'function') {
+                    if (!promised) {
                         return cb(err, result, i);
                     }
-                    return defer.resolve(result);
+                    return cb.resolve(result);
                 }
 
                 i += 1;
@@ -78,21 +82,27 @@ var multiCaching = function(caches, options) {
 
             cache.store.get(key, options, callback);
         }, function(err, result) {
-            if (typeof cb === 'function') {
-                cb(err, result);
+            if (!promised) {
+                return cb(err, result);
             }
 
-            if (err) {
-                return defer.reject(err);
-            }
-            defer.resolve(result);
+            return (err) ? cb.reject(err) : cb.resolve(result);
         });
 
-        return defer.promise;
+        if (promised) {
+            return cb.promise;
+        }
     }
 
     function setInMultipleCaches(caches, opts, cb) {
         opts.options = opts.options || {};
+
+        var promised = false;
+        if (!cb) {
+            promised = true;
+            cb = Promise.defer();
+        }
+
         async.each(caches, function(cache, next) {
             var _isCacheableValue = getIsCacheableValueFunction(cache);
 
@@ -102,16 +112,16 @@ var multiCaching = function(caches, options) {
                 next();
             }
         }, function(err, result) {
-            if (typeof cb === 'object') {
-                if (err) {
-                    cb.reject(err);
-                } else {
-                    cb.resolve(result);
-                }
-            } else if (typeof cb === 'function') {
+            if (promised) {
+                return (err) ? cb.reject(err) : cb.resolve(result);
+            } else {
                 cb(err, result);
             }
         });
+
+        if (promised) {
+            return cb.promise;
+        }
     }
 
     /**
@@ -257,11 +267,7 @@ var multiCaching = function(caches, options) {
             options: options
         };
 
-        var defer = Promise.defer();
-
-        setInMultipleCaches(caches, opts, cb || defer);
-
-        return defer.promise;
+        return setInMultipleCaches(caches, opts, cb);
     };
 
     /**