I'm getting a Object doesn't support this property or method error, does anyone know why?

I do have values plugged into userId, fname, lname, oname, sam, hasAccess

function Employee(id, fname, lname, oname, sam, access) {

    this.id = id;

    this.fname = fname;

    this.lname = lname;

    this.oname = oname

    this.sam = sam;

    this.access = access;

}



var emp = new Employee(userId, fname, lname, oname, sam, hasAccess);



var jsonstuff = emp.toSource(); //Breaking here

Although this link says its possible http://www.w3schools.com/jsref/jsref_toSource_date.asp