SOURCE

Function.prototype.call = function(context) {
  context = context || window;
  context.fn = this;
  
  var args = Array.prototype.slice.call(arguments, 1);
  
  let result = context.fn(...args);
  
  delete context.fn;
  
  return result;
};


Function.prototype.apply = function(context, args) {
  context = context || window;
  context.fn = this;
  
  let result = null;
  if(!args) {
    result = context.fn();
  } else {
    result = context.fn(...args);
  }
  
  delete context.fn;
  return result;
};