Question

Is it possible to write this flow control in JavaScript?

MyLib.get = function() { /* do something */ next(); };
MyLib.save = function() { /* do something */ next(); };
MyLib.alert = function() { /* do something */ next(); };

MyLib.flow([
  MyLib.get(),
  MyLib.save(),
  MyLib.alert()
], function() {
  // all functions were executed
});

Answer 1

Yes, but two things to know:

1. You should build the array from references to your functions. That means you leave off the (), because you just want to pass through the reference, not the result of calling the function!
2. You’re going to have to deal with the fact that getting references to functions from properties of an object will not “remember” the relationship to that object. Thus, the “flow” code would have no way to know how to invoke the functions with “MyLib” as the this context reference. If that’s important, you’ll want to create functions that run your “member” functions in the right context.

To run the functions in the right context, you can cobble together something like the “bind” function supplied by the Prototype framework (and also, among many others, Functional.js), or $.proxy() from jQuery. It’s not that hard and would probably look like this:

function bindToObject(obj, func) {
  return function() {
    func.apply(obj, arguments);
  }
}

then you’d use it like this:

MyLib.flow([
  bindToObject(MyLib, MyLib.get),
  bindToObject(MyLib, MyLib.save),
  bindToObject(MyLib, MyLib.alert)
]);

If you need for parameters to be passed in, you could modify “bindToObject”:

function bindToObject(obj, func) {
  var preSuppliedArgs = Array.prototype.slice.call(arguments, 2);
  return function() {
    func.apply(obj, preSuppliedArgs.splice(arguments));
  }
}

That assumes you’d want additional arguments passed when the “bound” function is called to be tacked on to the end of the argument list. In your case, I doubt you’d want to do that, so you could leave off that “splice()” call.