es6 去除小数点后，不四舍五入

 　1:  {
   2:      n = 52.123456;
   3:      //alert(typeof n);
   4:      alert(n);
   5:  }
   6:  //有符号右移
   7:  {
   8:      n = 52.123456;
   9:      var n2 = n >> 0;
  10:      //alert(typeof n2);
  11:      alert(n2);
  12:  }
  13:  //无符号右移
  14:  {
  15:      n = 52.123456;
  16:      var n3 = n >>> 0;
  17:      //alert(typeof n3);
  18:      alert(n3);
  19:  }
  20:  //左移0位
  21:  {
  22:      n = 52.123456;
  23:      var n4 = n << 0;
  24:      //alert(typeof n4);
  25:      alert(n4);
  26:  }
  27:  //按位或or
  28:  {
  29:      n = 52.123456;
  30:      var n5 = n | 0;
  31:      //alert(typeof n5);
  32:      alert(n5);
  33:  }
  34:  //按位异或xor
  35:  {
  36:      n = 52.123456;
  37:      var n6 = n ^ 0;
  38:      //alert(typeof n6);
  39:      alert(n6);
  40:  }