code: function StringRepeat(count) {
    CHECK_OBJECT_COERCIBLE(this, "String.prototype.repeat");
  
    var s = TO_STRING(this);
    var n = TO_INTEGER(count);
  
    if (n < 0 || n === INFINITY) throw MakeRangeError(kInvalidCountValue);
  
    // Early return to allow an arbitrarily-large repeat of the empty string.
    if (s.length === 0) return "";
  
    // The maximum string length is stored in a smi, so a longer repeat
    // must result in a range error.
    if (n > %_MaxSmi()) throw MakeRangeError(kInvalidCountValue);
  
    var r = "";
    while (true) {
      if (n & 1) r += s;
      n >>= 1;
      if (n === 0) return r;
      s += s;
    }
  }
docs: ES6, section 21.1.3.13