Method that returns property VS property direct access in javascript

Question

I have found that many javascript developers create methods that simply return a property like this :

function Obj (prop) {
    this.prop = prop; // public
}
Obj.prototype.getProp = function () {
    return this.prop;
};

While prop is public and can be accessed like this :

var a = obj.prop;

Moreover, I found that accessing an object property with a method is 121 times slower than accessing it directly (in Firefox)

var a, b,
    obj = new Obj(1);

a = obj.prop;
// ~6ns on Chrome
// ~5ns on Firefox

b = obj.getProp();
// ~6ns on Chrome (no difference)
// ~730ns on Firefox (122x slower...)

So my question is: should we always create methods that return properties or can we access properties directly? Is that antipattern?

Answer 1

Yes it's an antipattern. Since js doesn't have native getters and setters which will be crossbrowser, yet, you should create your own getters and setters like:

Obj.prototype.getProp = function () {
    return this.prop;
};

Yes, you still can access this prop directly, but now you doesn't have to. More on that. This way you can create private properties via closures:

function Foo() {
   var __yourPrivateProp = 'Bar';
   return {
           getyourPrivateProp: function () {
               return: __yourPrivateProp
           }
   };
}