3 files changed, 22 insertions, 3 deletions
diff --git a/lib/reduce.js b/lib/reduce.js
index 1a6c036..b7434f0 100644
--- a/lib/reduce.js
+++ b/lib/reduce.js
@@ -2,6 +2,7 @@ import eachOfSeries from './eachOfSeries';
 import noop from './internal/noop';
 import once from './internal/once';
 import wrapAsync from './internal/wrapAsync';
+import awaitify from './internal/awaitify'
 
 /**
  * Reduces `coll` into a single value using an async `iteratee` to return each
@@ -32,6 +33,7 @@ import wrapAsync from './internal/wrapAsync';
  * @param {Function} [callback] - A callback which is called after all the
  * `iteratee` functions have finished. Result is the reduced value. Invoked with
  * (err, result).
+ * @returns {Promise} a promise, if no callback is passed
  * @example
  *
  * async.reduce([1,2,3], 0, function(memo, item, callback) {
@@ -43,13 +45,15 @@ import wrapAsync from './internal/wrapAsync';
  *     // result is now equal to the last value of memo, which is 6
  * });
  */
-export default function reduce(coll, memo, iteratee, callback) {
+function reduce(coll, memo, iteratee, callback) {
     callback = once(callback || noop);
     var _iteratee = wrapAsync(iteratee);
-    eachOfSeries(coll, (x, i, iterCb) => {
+    return eachOfSeries(coll, (x, i, iterCb) => {
         _iteratee(memo, x, (err, v) => {
             memo = v;
             iterCb(err);
         });
     }, err => callback(err, memo));
 }
+export default awaitify(reduce, 4)
+
diff --git a/lib/reduceRight.js b/lib/reduceRight.js
index dd56a88..994eaf9 100644
--- a/lib/reduceRight.js
+++ b/lib/reduceRight.js
@@ -21,8 +21,9 @@ import reduce from './reduce';
  * @param {Function} [callback] - A callback which is called after all the
  * `iteratee` functions have finished. Result is the reduced value. Invoked with
  * (err, result).
+ * @returns {Promise} a promise, if no callback is passed
  */
 export default function reduceRight (array, memo, iteratee, callback) {
     var reversed = [...array].reverse();
-    reduce(reversed, memo, iteratee, callback);
+    return reduce(reversed, memo, iteratee, callback);
 }
diff --git a/test/es2017/awaitableFunctions.js b/test/es2017/awaitableFunctions.js
index 1656894..b51a23b 100644
--- a/test/es2017/awaitableFunctions.js
+++ b/test/es2017/awaitableFunctions.js
@@ -220,4 +220,18 @@ module.exports = function () {
         await async.mapValuesLimit(inputObj, 1, async (...args) => { calls.push(args) });
         expect(calls).to.eql([[1, 'a'], [2, 'b'], [3, 'c']])
     });
+
+
+    it('should return a Promise: reduce', async () => {
+        expect (async.reduce.name).to.contain('reduce')
+        const calls = []
+        await async.reduce(input, 1, async (...args) => calls.push(args));
+        expect(calls).to.eql([[1, 1], [1, 2], [2, 3]])
+    });
+    it('should return a Promise: reduceRight', async () => {
+        expect (async.reduceRight.name).to.contain('reduceRight')
+        const calls = []
+        await async.reduceRight(input, 1, async (...args) => calls.push(args));
+        expect(calls).to.eql([[1, 3], [1, 2], [2, 1]])
+    });
 };