Cleaner way for redirecting back to the Referrer

The 'back' special case has been moved from res.location() to a
new req.back getter. In the future, this will make it possible
to redirect to a regular 'back' page.

examples/auth/index.js

@@ -116,7 +116,7 @@ app.post('/login', function (req, res, next) {
         req.session.success = 'Authenticated as ' + user.name
           + ' click to <a href="/logout">logout</a>. '
           + ' You may now access <a href="/restricted">/restricted</a>.';
-        res.redirect('back');
+        res.redirect(req.back);
       });
     } else {
       req.session.error = 'Authentication failed, please check your '

examples/cookies/index.js

@@ -33,7 +33,7 @@ app.get('/', function(req, res){
 
 app.get('/forget', function(req, res){
   res.clearCookie('remember');
-  res.redirect('back');
+  res.redirect(req.back);
 });
 
 app.post('/', function(req, res){
@@ -43,7 +43,7 @@ app.post('/', function(req, res){
     res.cookie('remember', 1, { maxAge: minute })
   }
 
-  res.redirect('back');
+  res.redirect(req.back);
 });
 
 /* istanbul ignore next */

examples/route-separation/user.js

@@ -43,5 +43,5 @@ exports.update = function(req, res){
   var user = req.body.user;
   req.user.name = user.name;
   req.user.email = user.email;
-  res.redirect('back');
+  res.redirect(req.back);
 };

lib/request.js

@@ -498,6 +498,18 @@ defineGetter(req, 'xhr', function xhr(){
   return val.toLowerCase() === 'xmlhttprequest';
 });
 
+/**
+ * Return the referrer, or "/" if not present.
+ * Useful as argument to res.redirect().
+ *
+ * @return {String}
+ * @public
+ */
+
+defineGetter(req, 'back', function back(){
+  return this.get('Referrer') || '/';
+});
+
 /**
  * Helper function for creating a getter on an object.
  *

lib/response.js

@@ -789,7 +789,8 @@ res.location = function location(url) {
 
   // "back" is an alias for the referrer
   if (url === 'back') {
-    loc = this.req.get('Referrer') || '/';
+    deprecate('res.location("back"): Use res.location(req.back) instead');
+    loc = this.req.back;
   } else {
     loc = String(url);
   }

test/res.location.js

@@ -51,7 +51,7 @@ describe('res', function(){
         var app = express()
 
         app.use(function (req, res) {
-          res.location('back').end()
+          res.location(req.back).end()
         })
 
         request(app)
@@ -65,7 +65,7 @@ describe('res', function(){
         var app = express()
 
         app.use(function (req, res) {
-          res.location('back').end()
+          res.location(req.back).end()
         })
 
         request(app)
@@ -79,7 +79,7 @@ describe('res', function(){
         var app = express()
 
         app.use(function (req, res) {
-          res.location('back').end()
+          res.location(req.back).end()
         })
 
         request(app)
@@ -94,7 +94,7 @@ describe('res', function(){
         var app = express()
 
         app.use(function (req, res) {
-          res.location('back').end()
+          res.location(req.back).end()
         })
 
         request(app)