Function and method callbacks for simplifying error handling

safeFactory.js

// So we start with a function that will allow to create new functions that 
// convert errors into events. 

var safeFactory = function(emitter) {
  return function(fn) {
    return function(err,value) {
    if (err) { emitter.emit("error",err); }
    else fn(value);
    }
  }
};

// Then you can do:
// 
//     var safe = safeFactory(this);
//     
//       ...
//       
//     asyncThing(safe(myCallback));
//     
//     
// Or (assuming you have a library like underscore):
// 
//     asyncThing(safe(_.bind(this,myCallback)));
//     
// This opens the possibility of defining a function that defines a method 
// that converts an async call into a safe invocation.

var safeMethodFactory = function(object,method,async,callback) {
  return function() {
    var args = _(arguments); // converts arguments to an Array
    args.push(safe(_.bind(object,callback)));
    return async(args);
  }
};
// 
// So now you could do something like this:
// 
//     var A = function() {
//       this.readFile = safeMethodFactory(this,fs.readFile,this.parse);
//     }