stamp-privatize.md

@stamp/privatize

Makes all properties and optional methods private

Inspired by the private-class module. NOTE! Requires WeakMap, thus won't work in IE10.

This stamp (aka behavior) will create a proxy object. Its methods would delegate all the calls to the original object instance.

All the properties are made private. Methods privatization is optional and can be done via the privatizeMethods static function.

Usage

import Privatize from '@stamp/privatize';

import Auth from './stamps/auth';

const AuthWithPrivateProperties = Auth.compose(Privatize);

const AuthWithPrivatePropertiesAndMethod = Auth.compose(Privatize).privatizeMethods('setPassword');

Or if you don't want to import the stamp you can import only the method:

import {privatizeMethods} from '@stamp/privatize';
const AuthWithPrivatePropertiesAndMethod = Auth.compose(privatizeMethods('setPassword'));

Warning!

Every property you assign in the initializers will be private.

const Original = compose({
  initializers: function () {
    this.foo = 42; // THIS WILL BE PRIVATE
    this.bar = function () {}; // THIS WILL BE PRIVATE TOO
  }
});
Original().foo === undefined; 
Original().bar === undefined;

This is a neat feature since you don't need to use JS closures to hide variables from external users.

Example

let accessPassword, accessSetPassword;
const Original = compose({
  properties: {password: '123'},
  methods: {
    setPassword(value) { this.password = value; },
    checkAccess() {
      accessPassword = this.password;
      accessSetPassword = this.setPassword;
    }
  }
});

// Add Privatize behavior, additionally protect the 'setPassword' method 
const Stamp = Original.compose(Privatize).privatizeMethods('setPassword');

// All properties and the method 'setPassword' are undefined
const instance = Stamp();
expect(instance.password).toBeUndefined();
expect(instance.setPassword).toBeUndefined();

// But the 'checkAccess' method have access to the properties and 'setPassword'
instance.checkAccess();
expect(accessPassword).toBe('123');
expect(accessSetPassword).toBe(Original.compose.methods.setPassword);

Smart use of configuration

If you ever was thinking how cool if it was having configuration (and deepConfiguration) accessible in your method without explicitly exposing it through initializer, with privatize stamp you can simply do this. First make your own extension to Private stamp.

import Privatize from '@stamp/privatize';
const ConfiguredPrivatize = Privatize.compose({
  initializers: [(_, {stamp, instance}) => {
    instance.stampConfiguration = stamp.compose.configuration;
    instance.stampDeepConfiguration = stamp.compose.deepConfiguration;
  }]
})
export default ConfiguredPrivatize;

Then you can use for your other stamps and being able to access configuration within any method while still have it hidden from public sight.

compose(ConfiguredPrivatize, {
    configuration: {
        secret: 'mykey'
    },
    methods: {
        encrypt(value) {
          const { secret } = this.stampConfiguration;
          // run encryption with secret while it's still hidden from outside
        }
    }
})