How best to inherit from native JavaScript object? (Especially String)

Question

I\'m a long-time browser but a first time participator. If I\'m missing any etiquette details, please just let me know!

Also, I\'ve searched high and low, including this

Answer 1

This line is not valid:

this = n;

this is not a valid lvalue. Meaning, you cannot assign to the value referenced by this. Ever. It's just not valid javascript. Your example will work if you do:

var myString = function (n){
    this.prop = n;

    this.a = function (){
        alert(this.prop);
    };
}

myString.prototype = new String; // or String.prototype;

var x = new myString("foo");
x.a();

Regarding your workaround, you should realise that all you're doing is making a String object, augmenting a function property, and then calling it. There is no inheritance taking place.

For example, if you execute x instanceof myString in my example above it evaluates to true, but in your example it isn't, because the function myString isn't a type, it's just a regular function.