C# like properties in JavaScript

gistfile1.js

var createProperty = function(getSet) { 
    var _value;
    var autoImplement = {
        get: function() { return _value; },
        set: function(value) { _value = value; return _value; }
    };

    getSet = getSet || autoImplement;

    var get = getSet.get || function() { throw new Error('No get method defined for this property.'); },
        set = getSet.set || function() { throw new Error('No set method defined for this property.'); };

    return function(value) {
        if (value !== undefined)
            return set(value);

        return get();
    }; 
};

Well, what I was looking for something like:
myClass.customProperty = 123; // sets value
var value = myClass.customProperty; // gets value

Note the difference from the last two lines of your example.