Function.prototype.new

gistfile1.js

Function.prototype.new = function() {
    var obj = Object.create(this.prototype);
    this.apply(obj, arguments);
    return obj;
};

function Person(name) {
    this.setName(name);
}

Person.prototype.getName = function() {
    return this.name;
};

Person.prototype.setName = function(name) {
    this.name = name;
};

var david = Person.new('Dave');

david.getName(); // 'Dave'

You have 2 big issues. Both are related with the built-in constructors and Object.create. Even and every object inherits from Object.prototype, the objects have hidden internal behavior which depends on the type of the objects. e.g arrays have special setter, functions have call and construct methods etc.

Array.new();

Will create a new native object which inherits from Array.prototype but it would not be true array, because the internal behavior is not inherited trough the prototype chain.

The second problem is again with built-ins which have non-generic methods, e.g.:

String(String.new('')); // TypeError: String.prototype.toString is not generic

A better way to implement new is as follows: https://gist.github.com/aaditmshah/6269739

See the following StackOverflow answer: http://stackoverflow.com/a/17345713/783743