std-scope

Private and Protected Scope for JavaScript

One of the features that have always been painfully missing from JavaScript, in my opinion, is its conspicuous inability to use public, private, and protected to explicitly define the scope of class members. I would imagine that this particular quirk owes its origins to the same decisions that led to JavaScript not having a class keyword until ECMAScript 6 came about. Regardless of its origins, however, it's a feature whose absence I've always lamented — and a feature which many other developers have sought to emulate.

What do I mean when I say public, private, and protected scope?

If you've been programming for a while, then chances are pretty good that you've been exposed to these concepts before. The ability to define context-based access-controls on a class member is a pretty standard feature of Object-Oriented Programming languages. A typical implementation of these keywords would follow a fairly simple set of rules:

• A class member that has been declared public is available to everything that is able to access an instance of the class.
• A class member that has been declared private is only accessible within the class that instantiated the object.
• A class member that has been declared protected is only accessible within the object that owns the values.

Installation

Easy if you're using NPM:

npm install std-scope

Usage

Create the scope by running the create() command from within your module:

const { $protected, $private } = require('std-scope').create();

Accessing Variables

Protected and private variables can be accessed by passing the context into the $protected and $private functions, respectively:

$protected(this).value = 'test';
console.log($protected(this).value); // Prints "test"

You can also insert multiple values into the scope with one function call, by passing a dictionary of the new values as the second parameter of the function:

$private(this, { fname: 'Steven', lname: 'The Dev' });
console.log($private(this).fname); // 'Steven'
console.log($private(this).lname); // 'The Dev'

Disclaimer

There are two minor drawbacks to using this method:

1. A WeakMap is slower than attaching values directly to an object. In my testing, I've found that the performance hit allows around 1-million accesses per second.
2. The protected accessor can be used anywhere, so it's mostly security by obscurity.