private name objects shim
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Polyfill of private name objects. This implementation patches ES5 Object methods where possible to emulate private names as much as possible. Still in some cases private names can be discovered:

  • If Object methods from other JS contexts are used.
  • If properties are simply set like shown below, private names will be revealed by for iteration:

    object[secret] = value

    It is recommended to use Object.defineProperty or Object.defineProperties for defining private named properties. Those methods will make sure to mark property as non-enumerable so that such propertes won't be reavealed.


npm install name


var Name = require('name')
var secret = new Name()
function MyClass(privateData) {
  // do not do `this[secret] = privateData` do following instead
  Object.defineProperty(this, secret, {
    value: privateData
  }) = 'my'
MyClass.prototype = {
  doStuff: function() {
    /*...*/ this[secret] /*...*/

var my = new MyClass()
Object.keys(my) // => [ 'my' ]
Object.getOwnPropertyNames(my) // => [ 'my' ]

var names = []
for (var name in my) names.push(name)
names // => [ 'my' ]