gistfile1.js

"use strict";

var _tailCall = (function () {
  function Tail(func, args, context) {
    this.func = func;
    this.args = args;
    this.context = context;
  }
  Tail.prototype._isTailDescriptor = true;
  var isRunning = false;

  return function (func, args, context) {
    var result = new Tail(func, args, context);
    if (!isRunning) {
      isRunning = true;
      do {
        result = result.func.apply(result.context, result.args);
      } while (result instanceof Tail || result && result._isTailDescriptor);
      isRunning = false;
    } return result;
  };
})();

function format(x) {
  return _tailCall(x.toUpperCase, [], x);
}

function makeObj(arr) {
  return _tailCall(arr.reduce, [function (obj, x) {
    var upper = format(x);
    obj[x] = 1;
    obj[upper] = 2;

    return obj;
  }, {}], arr);
}

var result = makeObj(["yes", "no"]);

console.log(result);