Crockford's "Private Members in JavaScript"

crockford.js

// Public
function Constructor(...) {
  this.membername = value;
}
Constructor.prototype.membername = value;

// Private
function Constructor(...) {
  var that = this;
  var membername = value;
  function membername(...) {...}
}

// Privileged
function Constructor(...) {
  this.membername = function (...) {...};
}