Lazy properties for ES5

lazy-property.js

function lazyProperty(object, name, create) {
  Object.defineProperty(object, name, {
    configurable: true, // or false if defined on prototype objects
    enumerable: false,
    get: function() {
      return this[name] = create(this);
    },
    set: function(value) {
      Object.defineProperty(this, name, {
        configurable: true,
        enumerable: false,
        value: value,
        writable: true
      });
    }
  });
}