common api.js

// Super simplified sample library
fs.readFile = function (filename, another_arg, more args, callback) {
  callback(error, content);
}

// Curried
fs.readFile = function (filename, another_arg, more args) { return function (callback) {
  callback(error, content);
}}

// base arg with options hash
fs.readFile = function (filename, {encoding: "ascii"}, callback) {
  callback(error, content);
}

// Promise people could do this
promise(fs.readFile, "myfile").then(function (data) {...})
// Or even this
when(fs.readFile, "myfile", function (data) {...})
// Continuable people could do this
cont(fs.readFile, "myfile")(function (data) {...})