Add comments and avoid Array.fill

Polymer · Feb 27, 2019 · 567c10b · 567c10b
1 parent e8c24ff
commit 567c10b
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Showing 2 changed files with 19 additions and 9 deletions.
diff --git a/lib/utils/debounce.js b/lib/utils/debounce.js
@@ -123,6 +123,8 @@ let debouncerQueue = new Set();
  * @return {void}
  */
 export const enqueueDebouncer = function(debouncer) {
+  // Re-enqueued debouncers are put at the end of the queue; for Set, this
+  // means removing and re-adding, since forEach traverses insertion order
   if (debouncerQueue.has(debouncer)) {
     debouncerQueue.delete(debouncer);
   }
@@ -136,6 +138,8 @@ export const enqueueDebouncer = function(debouncer) {
  */
 export const flushDebouncers = function() {
   const didFlush = Boolean(debouncerQueue.size);
+  // If new debouncers are added while flushing, Set.forEach will ensure
+  // newly added ones are also flushed
   debouncerQueue.forEach(debouncer => {
     try {
       debouncer.flush();

diff --git a/test/unit/debounce.html b/test/unit/debounce.html
@@ -217,16 +217,22 @@
       const timeoutCallback = sinon.spy(() => actualCallbacks.push(timeoutCallback));
       enqueueDebouncer(Debouncer.debounce(null, timeOut, timeoutCallback));
       // Set of short-running debouncers enqueued in the middle of first set
-      const nestedCallbacks = new Array(150).fill().map((_, i) => sinon.spy(() =>
-        actualCallbacks.push(nestedCallbacks[i])));
+      const nestedCallbacks = [];
+      for (let i=0; i<150; i++) {
+        nestedCallbacks.push(sinon.spy(() =>
+          actualCallbacks.push(nestedCallbacks[i])));
+      }
       // First set of short-running debouncers
-      const microtaskCallbacks = new Array(150).fill().map((_, i) => sinon.spy(() => {
-        actualCallbacks.push(microtaskCallbacks[i]);
-        if (i === 125) {
-          nestedCallbacks.forEach(cb => 
-            enqueueDebouncer(Debouncer.debounce(null, microTask, cb)));
-        }
-      }));
+      const microtaskCallbacks = [];
+      for (let i=0; i<150; i++) {
+        microtaskCallbacks.push(sinon.spy(() => {
+          actualCallbacks.push(microtaskCallbacks[i]);
+          if (i === 125) {
+            nestedCallbacks.forEach(cb => 
+              enqueueDebouncer(Debouncer.debounce(null, microTask, cb)));
+          }
+        }));
+      }
       microtaskCallbacks.forEach(cb => 
         enqueueDebouncer(Debouncer.debounce(null, microTask, cb)));
       // Expect short before long