gistfile1.js

//
// Pattern 1
// Single message handler function

// Pros: task can implement message handling however it likes
// Cons: makes it harder to reason about what messages an object understands
 
// A possible default implementation
object.send = function(message) {
  if (typeof this[message.type] === 'function') {
    this[message.type](message);
  } else if (typeof this.anyMessage === 'function') {
    this.anyMessage(message);
  }
}

// But this would also be acceptable (transparent proxy)
// etc, etc
object.send = function(message) {
  otherObject.send(message);
}

//
// Pattern 2
// Externalisation of pattern 1's "default implementation"

// Pros: message handling is system defined so very easy to reason about.
//       because object layout is fixed, easy to send messages statically,
//       as a normal function call... e.g. object.foo()
// Cons: loss of flexibility

// send is system-level function 
function send(object, message) {
  if (typeof object[message.type] === 'function') {
    object[message.type](message);
  } else if (typeof object.anyMessage === 'function') {
    object.anyMessage(message);
  }
}