var restArgs = function(func, startIndex) {
  startIndex = startIndex == null ? func.length - 1 : +startIndex;
  return function() {
    var length = Math.max(arguments.length - startIndex, 0);
    var rest = Array(length);
    for (var index = 0; index < length; index++) {
      rest[index] = arguments[index + startIndex];
    }
    switch (startIndex) {
      case 0: return func.call(this, rest);
      case 1: return func.call(this, arguments[0], rest);
      case 2: return func.call(this, arguments[0], arguments[1], rest);
    }
    var args = Array(startIndex + 1);
    for (index = 0; index < startIndex; index++) {
      args[index] = arguments[index];
    }
    args[startIndex] = rest;
    return func.apply(this, args);
  };
};

var delay = restArgs(function(func, wait, args) {
  return setTimeout(function(){
    return func.apply(null, args);
  }, wait);
});

var sayHi = function(){
    console.log("Hello");
}
delay(sayHi, 200, 1, 2, 3);

另外： 为什么 restArgs 的返回函数中 arguments 的值是 [sayHi, 200, 1, 2, 3] ？