From c626c99a14e175f46103cea5d19aaf2dc63ed893 Mon Sep 17 00:00:00 2001
From: Graeme Yeates <yeatesgraeme@gmail.com>
Date: Fri, 11 Nov 2016 16:28:02 -0500
Subject: Handle iterators

---
 lib/internal/filter.js | 13 ++++++++-----
 mocha_test/filter.js   | 31 +++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/lib/internal/filter.js b/lib/internal/filter.js
index 454cc54..e191524 100644
--- a/lib/internal/filter.js
+++ b/lib/internal/filter.js
@@ -1,7 +1,8 @@
-import each from 'lodash/each';
 import isArrayLike from 'lodash/isArrayLike';
 import noop from 'lodash/noop';
+
 import once from './once';
+import iterator from './iterator';
 
 export default function _filter(eachfn, coll, iteratee, callback) {
     callback = once(callback || noop);
@@ -14,11 +15,13 @@ export default function _filter(eachfn, coll, iteratee, callback) {
     }, function (err) {
         if (err) return callback(err);
         var result = [];
-        each(coll, function(_, index) {
-            if (truthValues[index] === true) {
-                result.push(coll[index]);
+        var nextElem = iterator(coll);
+        var elem;
+        while ((elem = nextElem()) !== null) {
+            if (truthValues[elem.key] === true) {
+                result.push(elem.value);
             }
-        });
+        }
         callback(null, result);
     });
 }
diff --git a/mocha_test/filter.js b/mocha_test/filter.js
index 05d9d99..8f13620 100644
--- a/mocha_test/filter.js
+++ b/mocha_test/filter.js
@@ -53,6 +53,37 @@ describe("filter", function () {
         });
     });
 
+    if (typeof Symbol === 'function' && Symbol.iterator) {
+        function makeIterator(array){
+            var nextIndex;
+            let iterator = {
+                next: function(){
+                    return nextIndex < array.length ?
+                       {value: array[nextIndex++], done: false} :
+                       {done: true};
+                }
+            };
+            iterator[Symbol.iterator] = function() {
+                nextIndex = 0; // reset iterator
+                return iterator;
+            };
+            return iterator;
+        }
+
+        it('filter iterator', function(done){
+            var a = makeIterator([500, 20, 100]);
+            async.filter(a, function(x, callback) {
+                setTimeout(function() {
+                    callback(null, x > 20);
+                }, x);
+            }, function(err, results){
+                expect(err).to.equal(null);
+                expect(results).to.eql([500, 100]);
+                done();
+            });
+        });
+    }
+
     it('filter error', function(done){
         async.filter([3,1,2], function(x, callback){
             callback('error');
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