判断字符的一些js代码收集

/**
 *  rief 求得一个字符串的ANSI字符串长度
 *  param value 传入的UNICODE字符串
 *  eturn 返回字符串的ANSI字符串长度
 */
function ByteWordCount(value) {
  var txt = value;
  txt = txt.replace(/(<.*?>)/ig,''); 
  txt = txt.replace(/([u0391-uFFE5])/ig,'11');
  return txt.length;
}

/**
 *  rief 判断一个字符是否是字母
 *  param ch 要判断的字符
 *  eturn true 是 false 不是
 */
function isAlpha(ch) {
  if(ch >= "a" && ch <= "z") return true;
  if(ch >= "A" && ch <= "Z") return true;
  return false;
}

/**
 *  rief 判断一个字符是否是数字
 *  param ch 要判断的字符
 *  eturn true 是 false 不是
 */
function isNumber(ch) {
  if(ch >= "0" && ch <= "9") return true;
  return false;
}

/**
 *  rief 判断一个字符是否是可打印标点符号
 *  param ch 要判断的字符
 *  eturn true 是 false 不是
 */
function isSpecial(ch) {
  var special = new Array("!","""","#","$","%","&","'","(",")","*","+",",","-",".","/",":",";","<","=",">","?","@","[","/","]","^","_","`","{","|","}","~")
  for(var i=0;i<special.length;++i)
    if(ch == special[i]) return true;
  return false;
}

function CheckValidStr(value)
{
  var count=0;
  for(var i=0;i<value.length;++i)
  {
    var ch = value.charAt(i);
    if(isAlpha(ch)||isNumber(ch)||isSpecial(ch))
      count++;
    else
      count=0;
    if(count>20)
    {
      return false;
    }
  }
  return true;
}