javascript - function prototype inheritance with new keyword -

i making sure understood javascript's new , prototype keywords correctly simple code put not behaving expect.

var classa = function() {     return {         shout: function() {              alert("i can shout");         }     }; }; classa.prototype.shoutlouder = function() {      alert("i can shout"); };  var instance = new classa(); instance.shout();  // why not available? instance.shoutlouder(); 

when instance variable attempts invoke shoutlouder it's failing "uncaught typeerror: instance.shoutlouder not function".

but, in mozilla docs, says when using new create object:

a new object created, inheriting foo.prototype.

where wrong in understanding?

here jsbin above code-snippit.

you're losing access function's (class') prototype object because you're returning new object out of function:

var classa = function() {     return {         shout: function() {              alert("i can shout");         }     }; }; 

whereas should doing:

var classa = function() {     this.shout = function() {         alert("i can shout");     }; }; 

this still give access prototype object (and delegation chain still work) because new keyword return 'this' class.