[Riim]

function User(properties) {
		var that = this;
        for (var i in properties) {
         
            (function(i){
             
                that["get" + i] = function() {
                    return properties[i];
                }
                 
                that["set" + i] = function(val) {
                    properties[i] = val;
                }
            })(i);
        }       
    }
     
var user = new User({
    name : "hat_tab",
    age : 100500
});
     
alert(user.getname());

у внутренней функции свой this.