Add documentation about World to README

README.md

@@ -122,18 +122,38 @@ Support files let you setup the environment in which steps will be run, and defi
 // features/support/world.js
 
 var zombie = require('zombie');
-var World = function(callback) {
+var World = function World(callback) {
   this.browser = new zombie.Browser(); // this.browser will be available in step definitions
 
   this.visit = function(url, callback) {
     this.browser.visit(url, callback);
   };
 
-  callback(); // tell Cucumber we're finished
+  callback(); // tell Cucumber we're finished and to use 'this' as the world instance
 };
 exports.World = World;
 ```
 
+It is possible to tell Cucumber to use another object instance than the constructor:
+
+``` javascript
+// features/support/world.js
+
+var zombie = require('zombie');
+var WorldConstructor = function WorldConstructor(callback) {
+  this.browser = new zombie.Browser(); // this.browser will be available in step definitions
+
+  var world = {
+    visit: function(url, callback) {
+      this.browser.visit(url, callback);
+    }
+  };
+
+  callback(world); // tell Cucumber we're finished and to use our world object instead of 'this'
+};
+exports.World = WorldConstructor;
+```
+
 #### Step Definitions
 
 Step definitions are the glue between features written in Gherkin and the actual *SUT* (*system under test*). They are written in JavaScript.