获取字符串字节长度跟截取字符串字节长度

//获取字符串的字节长度
function getStringByteLength(str){
  var realLength = 0;
  for (var i = 0; i < str.length; i++)
  {
    charCode = str.charCodeAt(i);
    if (charCode >= 0 && charCode <= 128)
      realLength += 1;
    else
      realLength += 2;
  }
  return realLength;
}
//按字节截取字符串长度
function cutOutStringByteLength(str,long) {
  var seeString = [];
  var countByteLength = 0;
  for(var i=0;i<str.length;i++){
    var charCode = str.charCodeAt(i);
    if (charCode >= 0 && charCode <= 128){
      countByteLength += 1;
    }else{
      countByteLength += 2;
    }
    if (countByteLength <= long){
      seeString.push(str[i]);
    }
  }
  return seeString.join("");
}