Ensure _.debounce queues a trailing call after maxWait. [closes #2229]

jdalton · jdalton · commit e60e97c03fda · 2016-04-10T20:50:51.000-07:00
diff --git 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
@@ -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);
 

Original file line number	Diff line number	Diff line change
`@@ -9436,6 +9436,9 @@`
`9436`	`9436`	`timerId = setTimeout(timerExpired, wait);`
`9437`	`9437`	`return invokeFunc(lastCallTime);`
`9438`	`9438`	`}`
	`9439`	`+ if (timerId === undefined) {`
	`9440`	`+ timerId = setTimeout(timerExpired, wait);`
	`9441`	`+ }`
`9439`	`9442`	`return result;`
`9440`	`9443`	`}`
`9441`	`9444`	`debounced.cancel = cancel;`