Merge pull request kriskowal#686 from kahnjw/add_noconflict

Add Q.noConflict function

q.js

@@ -56,8 +56,18 @@
 
     // <script>
     } else if (typeof self !== "undefined") {
+        // Get the `window` object, save the previous Q global
+        // and initialize Q as a global.
+        var previousQ = self.Q;
         self.Q = definition();
 
+        // Add a noConflict function so Q can be removed from the
+        // global namespace.
+        self.Q.noConflict = function () {
+            self.Q = previousQ;
+            return this;
+        };
+
     } else {
         throw new Error("This environment was not anticipated by Q. Please file a bug.");
     }
@@ -2022,6 +2032,10 @@ Promise.prototype.nodeify = function (nodeback) {
     }
 };
 
+Q.noConflict = function() {
+    throw new Error("Q.noConflict only works when Q is used as a global");
+};
+
 // All code before this point will be filtered from stack traces.
 var qEndingLine = captureLine();
 

spec/q-spec.js

@@ -2491,6 +2491,36 @@ describe("node support", function () {
 
 });
 
+describe("browser support", function () {
+    var _Q;
+
+    beforeEach(function() {
+        _Q = Q;
+    });
+
+    afterEach(function() {
+        Q = _Q;
+    });
+
+    it("sets the global Q object to its original value", function() {
+        if (typeof window !== 'undefined') {
+            // If window is not undefined, the tests are running in the browser
+            // assert that Q.noConflict returns window.Q to it's initial value
+            // In this context the original value of Q is undefined
+            Q.noConflict();
+            expect(Q).toEqual(undefined);
+        }
+    });
+
+    it("throws an error if Q.noConflict is called in node", function () {
+        if (typeof window === 'undefined') {
+            // If window is undefined the tests are being run in node, and
+            // Q.noConflict should throw an error
+            expect(Q.noConflict).toThrow();
+        }
+    });
+});
+
 describe("isPromise", function () {
     it("returns true if passed a promise", function () {
         expect(Q.isPromise(Q(10))).toBe(true);