js_exam_tests.js

// [1,2,3,4,5].duplicator()
Array.prototype.duplicator = function() {
  var arr = this;
  if (!this.length) return;
  Array.prototype.map.call(this, function(el){ arr.push(el); });
  return arr;
}

// sum(1)(2)(3)();
function sum(x) {
  return function(y) {
    if (!y) return x;
      else return sum(x + y);
    };
}

// a.b.c.d -> a: { b: { c: { d: null}}}
var n = "a.b.c.d",
  z = n.split("."),
  s = {};
function gi(obj){
  var o = Object.getOwnPropertyNames(obj);
  if (o.length && Object.getOwnPropertyNames(obj[o]).length)
    return gi(obj[o]);
  else
    return o.toString();
}
// ...