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JavaScript prototype problem

If I call myRobot.Speak.sayHi() it always returns undefined. Please, what am I doing wrong? Thanks for reply!

var Factory = (function() {
 // Constructor 
 var Robot = function() {
 };
 // Public
 return {
 extendRobot: function(power, methods) {
 Robot.prototype[power] = methods;
 },
 createRobot: function() {
 return new Robot();
 }
 };
}());
Factory.extendRobot('Speak', {
 sayHi: function() {
 return 'Hi, ' + this.name;
 }
});
var myRobot = Factory.createRobot();
myRobot.name = 'Robin';
myRobot.Speak.sayHi() // => ‘Hi, Robin’

Answer*

createRobot: function() {
 var r = new Robot();
 for (var k in r.Speak) {
 if (typeof r.Speak[k] === "function") {
 r.Speak[k] = r.speak[k].bind(r);
 }
 }
 return r;
 }
 
Rather then returning a new robot, make sure to bind all the methods in your powers to the robot.

To avoid hard coding in the loops try this:

 Robot.powers = [];
 ...
 extendRobot: function(power, methods) {
 Robot.powers.push(power);
 Robot.prototype[power] = methods;
 },
 createRobot: function() {
 var robot = new Robot();
 Robot.powers.forEach(function(power) {
 for (var method in robot[power]) {
 if (typeof robot[power][method] === "function") {
 robot[power][method] = robot[power][method].bind(robot);
 }
 }
 });
 return robot;
 }

This relies on [Function.prototype.bind][1] so use the [ES5 shim][2] or use [underscore][3] for supporting old browsers (IE<9)

 [1]: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/bind
 [2]: https://github.com/kriskowal/es5-shim
 [3]: http://documentcloud.github.com/underscore/

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JavaScript prototype problem

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