Javascript automatic getter/setters (John Resig Book)

Question

I\'m reading \"Pro Javascript Techniques\" from John Resig, and I\'m confused with an example. This is the code:

// Create a new user object that accepts an          


        

Answer 1

I think it's best not to use the new keyword at all when working in JavaScript.

This is because if you then instantiate the object without using the new keyword (ex: var user = User()) by mistake, *very bad things will happen...*reason being that in the function (if instantiated without the new keyword), the this will refer to the global object, ie the window...

So therefore, I suggest a better way on how to use class-like objects.

Consider the following example :

var user = function (props) {
    var pObject = {};
    for (p in props) {
        (function (pc) {
            pObject['set' + pc] = function (v) {
                props[pc] = v;
                return pObject;
            }
            pObject['get' + pc] = function () {
                return props[pc];
            }
        })(p);
    }
    return pObject;
}

In the above example, I am creating a new object inside of the function, and then attaching getters and setters to this newly created object.

Finally, I am returning this newly created object. Note that the the this keyword is not used anywhere

Then, to 'instantiate' a user, I would do the following:

var john = user({name : 'Andreas', age : 21});
john.getname(); //returns 'Andreas'
john.setage(19).getage(); //returns 19

The best way to avoid falling into pitfalls is by not creating them in the first place...In the above example, I am avoiding the new keyword pitfall (as i said, not using the new keyword when it's supposed to be used will cause bad things to happen) by not using new at all.