Javascript parent function context

Question

When defining functions like this:

appName.Test = {
  init: function() {
    (...)
    .then(function(param1) {
      this.parameter1 = param1; // does NOT work ??
      appName.Test.parameter1 = param1; // does work
      this.foo();
    });
  }
}

How to define param1 at the "Test" level (context)? (this/parent.parameter1 do not work).

Method that does work "looks wrong" to me, is this correct way?. I need to define this variable at the Test context because it is used in other Test's methods..