object.__defineGetter__

obj.__defineGetter__(prop, func)

// Non-standard and deprecated way

var o = {};
o.__defineGetter__('gimmeFive', function() { return 5; }
console.log(o.gimmeFive // 5


// Standard-compliant ways

// Using the get operator
var o = { get gimmeFive() { return 5; } };
console.log(o.gimmeFive // 5

// Using Object.defineProperty
var o = {};
Object.defineProperty(o, 'gimmeFive', {
  get: function() {
    return 5;
  }
}
console.log(o.gimmeFive // 5