makeFoo = function() {
  var helper   = function(x, y) { return x + y },
      msgCount = 0
  return {
    receive: function(message) {
      msgCount++
      switch (message.name) {
        case 'add':    return helper(message.x, message.y)
        case 'sub':    return helper(message.x, -message.y)
        case 'stats':  return alert('message count = ' + msgCount)
        default:       throw 'message not understood: ' + message.name 
      }
    }
  }
}
foo = makeFoo()
foo.receive({name: "add", x: 35, y: 7})
foo.receive({name: "sub", x: 3,  y: 4})
foo.receive({name: "stats"})


makeFoo = function() {
  var helper   = function(x, y) { return x + y },
      msgCount = 0
  return function(message) {
      msgCount++
      switch (message.name) {
        case 'add':    return helper(message.x, message.y)
        case 'sub':    return helper(message.x, -message.y)
        case 'stats':  return alert('message count = ' + msgCount)
        default:       throw 'message not understood: ' + message.name 
      }
  }
}
foo = makeFoo()
foo({name: "add", x: 35, y: 7})
foo({name: "sub", x: 3,  y: 4})
foo({name: "stats"})