Question

I am wondering about javascript prototype. I know that prototyping enables the user to add new properties and methods to a constructor or an object.

I have used the following several times:

function Example() {}
Example.prototype.add = function () {};
Example.prototype.sub = someVar;

This way I can use Example.add as a function and Example.sub as an element of object.
But happens when someone writes something like this

Example.prototype = function() {
                    //Code
                    };

Any help?

Answer 1

Let’s take a look at a simple example:

 var Person = function(args){
     this.init(args);
 }

When defining a few methods for the person prototype we would do this:

 Person.prototype = {
     getAge : function(){},
     nickname : "R2D2"
 };

Or

 Person.prototype.getAge = function() {...};
 Person.prototype.nickName= "R2D2";

Both do the same thing. I prefer the first version because it’s easier to read and needs less characters to write ( making the footprint of my code smaller ).

The only reason I could think of for using

 Person.prototype = function(){}

is to create a private scope available only to the prototype of the Person. But this requires a self executing function which returns an object.

 Person.prototype = (function(){
    var theAnswerToEverything = 42;
    return {
        getTheAnswerToEverything : function(){
           return theAnswerToEverything;
        }
    };
 })();

theAnswerToEverything will be a variable usable only by the methods of the Persons prototype. More complex examples could be created by using the same principle.