Added an RSVP.all method, along with documentation and tests

README.md

@@ -137,6 +137,27 @@ getJSON("/post/1.json").then(function(post) {
 });
 ```
 
+## Arrays of promises
+
+Sometimes you might want to work with many promises at once. If you
+pass an array of promises to the `all()` method it will return a new
+promise that will be fulfilled when all of the promises in the array
+have been fulfilled; or rejected immediately if any promise in the array
+is rejected.
+
+```javascript
+var postIds = [2, 3, 5, 7, 11, 13];
+var promises = [];
+
+for(var i = 0; i < postIds.length; i++) {
+	promises.push(getJSON("/post/" + postIds[i] + ".json"));
+}
+
+RSVP.all(promises).then(function(posts) {
+	// posts contains an array of results for the given promises
+});
+```
+
 ## TaskJS
 
 The [TaskJS](http://taskjs.org/) library makes it possible to take

lib/rsvp.js

@@ -233,7 +233,33 @@ function reject(promise, value) {
   });
 }
 
+function all(promises) {
+	var i, results = [];
+	var allPromise = new Promise();
+	var remaining = promises.length;
+
+	var resolver = function(index) {
+		return function(value) {
+			resolve(index, value);
+		};
+	};
+	var resolve = function(index, value) {
+		results[index] = value;
+		if (--remaining === 0) {
+			allPromise.resolve(results);
+		}
+	};
+	var reject = function(error) {
+		allPromise.reject(error);
+	};
+
+	for (i = 0; i < remaining; i++) {
+		promises[i].then(resolver(i), reject);
+	}
+	return allPromise;
+}
+
 EventTarget.mixin(Promise.prototype);
 
-RSVP = { async: async, Promise: Promise, Event: Event, EventTarget: EventTarget };
+RSVP = { async: async, Promise: Promise, Event: Event, EventTarget: EventTarget, all: all };
 export = RSVP;

tests/extension-tests.js

+/*global RSVP, describe, specify, assert */
+describe("RSVP extensions", function() {
+  describe("RSVP.all", function() {
+    specify('it should exist', function() {
+      assert(RSVP.all);
+    });
+
+    specify('fulfilled only after all of the other promises are fulfilled', function(done) {
+      var first = new RSVP.Promise();
+      var second = new RSVP.Promise();
+
+      setTimeout(function() {
+        first.resolve(true);
+      }, 0);
+
+      setTimeout(function() {
+        second.resolve(true);
+      }, 0);
+
+      RSVP.all([first, second]).then(function() {
+        assert(first.isResolved);
+        assert(second.isResolved);
+        done();
+      });
+    });
+
+    specify('rejected as soon as a promise is rejected', function(done) {
+      var first = new RSVP.Promise();
+      var second = new RSVP.Promise();
+
+      setTimeout(function() {
+        first.reject({});
+      }, 0);
+
+      setTimeout(function() {
+        second.resolve(true);
+      }, 5000);
+
+      RSVP.all([first, second]).then(function() {
+        assert(false);
+      }, function() {
+        assert(first.isRejected);
+        assert(!second.isResolved);
+        done();
+      });
+    });
+
+    specify('passes the resolved values of each promise to the callback in the correct order', function(done) {
+      var first = new RSVP.Promise();
+      var second = new RSVP.Promise();
+      var third = new RSVP.Promise();
+
+      third.resolve(3);
+      first.resolve(1);
+      second.resolve(2);
+
+      RSVP.all([first, second, third]).then(function(results) {
+        assert(results.length === 3);
+        assert(results[0] === 1);
+        assert(results[1] === 2);
+        assert(results[2] === 3);
+        done();
+      });
+    });
+  });
+});

tests/index.html

@@ -28,6 +28,7 @@
   <script src="../promises-tests/lib/tests/helpers/testThreeCases.js"></script>
   <script>window.exports = undefined;</script>
   <script>mocha.setup({ ui: 'bdd', timeout: 200 })</script>
+  <script src="extension-tests.js"></script>
   <script src="../promises-tests/lib/tests/3.2.1.js"></script>
   <script src="../promises-tests/lib/tests/3.2.2.js"></script>
   <script src="../promises-tests/lib/tests/3.2.3.js"></script>