Merge pull request #365 from margelo/@szymon/use_map_for_pending_promise

Use map for keeping pending promises

lib/OnyxCache.js

@@ -34,9 +34,11 @@ class OnyxCache {
         /**
          * @private
          * Captured pending tasks for already running storage methods
-         * @type {Record<string, Promise>}
+         * Using a map yields better performance on operations such a delete
+         * https://www.zhenghao.io/posts/object-vs-map
+         * @type {Map<string, Promise>}
          */
-        this.pendingPromises = {};
+        this.pendingPromises = new Map();
 
         // bind all public methods to prevent problems with `this`
         _.bindAll(
@@ -133,7 +135,7 @@ class OnyxCache {
      * @returns {*}
      */
     hasPendingTask(taskName) {
-        return isDefined(this.pendingPromises[taskName]);
+        return isDefined(this.pendingPromises.get(taskName));
     }
 
     /**
@@ -145,7 +147,7 @@ class OnyxCache {
      * @returns {Promise<T>}
      */
     getTaskPromise(taskName) {
-        return this.pendingPromises[taskName];
+        return this.pendingPromises.get(taskName);
     }
 
     /**
@@ -157,11 +159,13 @@ class OnyxCache {
      * @returns {Promise<T>}
      */
     captureTask(taskName, promise) {
-        this.pendingPromises[taskName] = promise.finally(() => {
-            delete this.pendingPromises[taskName];
+        const returnPromise = promise.finally(() => {
+            this.pendingPromises.delete(taskName);
         });
 
-        return this.pendingPromises[taskName];
+        this.pendingPromises.set(taskName, returnPromise);
+
+        return returnPromise;
     }
 
     /**