Calling a Javascript member function of an object named in a variable

Question

I have the following so-called Revealing Module Pattern and I want to call the function a inside function b using a variable. How can

Answer 1

foo = function() {
    var inner = {
      a : function() {
      }
    };

    b = function() {
        memberName = 'a';
        // Call a() using value stored in variable `memberName`.
        inner[memberName]();
    }

    return {b: b};
}();