Array.prototype.slice = function(start, end){
  function ToInteger(num){
    //ToNumber
    num = +num;
    //NaN
    if (num !== num) return 0;
    if ((num === 0) || (num === Number.POSITIVE_INFINITY) || (num === Number.NEGATIVE_INFINITY) ){
      return num;
    }
    if (num > 0) {
      return Math.floor(num);
    } else {
      return -Math.floor(-num);
    }
  }

  //ToObject
  if (this == null) throw new TypeError;
  var obj = Object(this);

  var arr = [];

  var lenVal = obj.length;

  // ToUint32
  var len = lenVal >>> 0;

  var relativeStart = ToInteger(start);
  var k;
  if (relativeStart < 0) {
    k = Math.max(len + relativeStart, 0);
  } else {
    k = Math.min(relativeStart, len);
  }

  var relativeEnd;
  if (end === undefined) {
    relativeEnd = len;
  } else {
    relativeEnd = ToInteger(end);
  }

  //仕様書ではfinalだけど、予約語なので回避
  var final_;
  if (relativeEnd < 0) {
    final_ = Math.max(len + relativeEnd, 0);
  } else {
    final_ = Math.min(relativeEnd, len);
  }

  var n = 0, kPresent, kValue;
  while (k < final_) {
    //[[HasProperty]]
    kPresent = k in obj;
    if (kPresent) {
      kValue = obj[k];
      arr[n] = kValue;
    }
    ++k;
    ++n;
  }

  return arr;
};