V8 Microtask Queue & API

src/promise.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 155 matching lines @@
       break;
   }
   return deferred.promise;
 }
 
 function PromiseCatch(onReject) {
   return this.chain(UNDEFINED, onReject);
 }
 
 function PromiseEnqueue(value, tasks) {
-  promiseEvents.push(value, tasks);
+  GetMicrotaskQueue().push(function() {
+    for (var i = 0; i < tasks.length; i += 2) {
+      PromiseHandle(value, tasks[i], tasks[i + 1])
+    }
+  });
+
   %SetMicrotaskPending(true);
 }
 
-function PromiseMicrotaskRunner() {
-  var events = promiseEvents;
-  if (events.length > 0) {
-    promiseEvents = new InternalArray;
-    for (var i = 0; i < events.length; i += 2) {
-      var value = events[i];
-      var tasks = events[i + 1];
-      for (var j = 0; j < tasks.length; j += 2) {
-        var handler = tasks[j];
-        var deferred = tasks[j + 1];
-        try {
-          var result = handler(value);
-          if (result === deferred.promise)
-            throw MakeTypeError('promise_cyclic', [result]);
-          else if (IsPromise(result))
-            result.chain(deferred.resolve, deferred.reject);
-          else
-            deferred.resolve(result);
-        } catch(e) {
-          // TODO(rossberg): perhaps log uncaught exceptions below.
-          try { deferred.reject(e) } catch(e) {}
-        }
-      }
-    }
+function PromiseHandle(value, handler, deferred) {
+  try {
+    var result = handler(value);
+    if (result === deferred.promise)
+      throw MakeTypeError('promise_cyclic', [result]);
+    else if (IsPromise(result))
+      result.chain(deferred.resolve, deferred.reject);
+    else
+      deferred.resolve(result);
+  } catch(e) {
+    // TODO(rossberg): perhaps log uncaught exceptions below.
+    try { deferred.reject(e) } catch(e) {}
   }
 }
-RunMicrotasks.runners.push(PromiseMicrotaskRunner);
 
 
 // Multi-unwrapped chaining with thenable coercion.
 
 function PromiseThen(onResolve, onReject) {
   onResolve = IS_UNDEFINED(onResolve) ? PromiseIdResolveHandler : onResolve;
   var that = this;
   var constructor = this.constructor;
   return this.chain(
     function(x) {
@@ skipping 90 matching lines @@
     "cast", PromiseCast
   ]);
   InstallFunctions($Promise.prototype, DONT_ENUM, [
     "chain", PromiseChain,
     "then", PromiseThen,
     "catch", PromiseCatch
   ]);
 }
 
 SetUpPromise();