From e60e97c03fda22d4dfea84e07022183990cf20df Mon Sep 17 00:00:00 2001
From: John-David Dalton <john.david.dalton@gmail.com>
Date: Sun, 10 Apr 2016 19:53:34 -0700
Subject: [PATCH] Ensure `_.debounce` queues a trailing call after `maxWait`.
 [closes #2229]

---
 lodash.js    |  3 +++
 test/test.js | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/lodash.js b/lodash.js
index 4c2315455..bac9c7544 100644
--- a/lodash.js
+++ b/lodash.js
@@ -9436,6 +9436,9 @@
           timerId = setTimeout(timerExpired, wait);
           return invokeFunc(lastCallTime);
         }
+        if (timerId === undefined) {
+          timerId = setTimeout(timerExpired, wait);
+        }
         return result;
       }
       debounced.cancel = cancel;
diff --git a/test/test.js b/test/test.js
index 273e8bc19..4a1866d19 100644
--- a/test/test.js
+++ b/test/test.js
@@ -4248,6 +4248,29 @@
       }, 1);
     });
 
+    QUnit.test('should queue a trailing call for subsequent debounced calls after `maxWait`', function(assert) {
+      assert.expect(1);
+
+      var done = assert.async();
+
+      var callCount = 0;
+
+      var debounced = _.debounce(function() {
+        ++callCount;
+      }, 64, { 'maxWait': 64 });
+
+      debounced();
+
+      lodashStable.times(20, function(index) {
+        setTimeout(debounced, 54 + index);
+      });
+
+      setTimeout(function() {
+        assert.strictEqual(callCount, 2);
+        done();
+      }, 160);
+    });
+
     QUnit.test('should cancel `maxDelayed` when `delayed` is invoked', function(assert) {
       assert.expect(2);