Function.prototype.promisify.js

// Function.prototype.promisify
(function() {
  "use strict";
  
  if (Function.prototype.promisify) {
    console.error("Function.prototype.promisify() already exists");
    return;
  }
  
  var promiseFactory = function(context, f) {
    throw "promisify factory not set";
  };
  
  Function.prototype.promisify = function(context) {
    return promiseFactory(context, this);
  };
  
  Function.prototype.promiseCall = function() {
    var context = Array.prototype.shift.call(arguments);
    return this.promiseApply(context, arguments);
  };
  
  Function.prototype.promiseApply = function(context, args) {
    return (this.promisify(context)).apply(context, args);
  };
  
  window.initPromiseFactory = function(factory) {
    promiseFactory = factory;
  };
  
  // aliases
  Function.prototype.pCall = Function.prototype.promiseCall;
  Function.prototype.pApply = Function.prototype.promiseApply;
})();

// Factory Example
(function() {
  "use strict";
  
  function jqueryDeferredFactory(context, f) {
    return function() {
      if (!context) {
        context = this;
      }
      return $.Deferred().resolveWith(context, arguments).then(f);
    };
  }
  
  window.initPromiseFactory(jqueryDeferredFactory);
})();

// Example #1
(function() {
  function retIt(it) {
    return it;
  }
  
  function printIt(it) {
    console.log(it);
  }
  
  var retItPromisified = retIt.promisify();
  retItPromisified("it").then(printIt);
  
  retIt.promiseCall(null, "it 2").then(printIt);
  
  retIt.promiseApply(null, ["it 3"]).then(printIt);
  
  var csv = "c,s,v";
  csv.split.promiseCall(csv, ",").then(printIt);
  
  String.prototype.promiseSplit = String.prototype.split.promisify();
  "a,b,c".promiseSplit(",").then(printIt);
})();

// Example #2
(function() {
  var original = 5;

  function doubleIt(num) { return num * 2; }
  
  function addNine(num) { return num + 9; }
  
  function subtractThree(num) { return num - 3; }
  
  function divideByTwo(num) { return num / 2; }
  
  function subtractOriginal(num) { return num - original; }
  
  function printAndReturnIt(it) {
    console.log(it);
    return it;
  }
  
    printAndReturnIt.promiseCall(null, original)
    .then(doubleIt)
    .then(printAndReturnIt)
    .then(addNine)
    .then(printAndReturnIt)
    .then(subtractThree)
    .then(printAndReturnIt)
    .then(divideByTwo)
    .then(printAndReturnIt)
    .then(subtractOriginal)
    .then(printAndReturnIt);
})();