JavaScript字符串处理方法及其应用场景

//计算字符串长度
String.prototype.strLen = function() {
    var len = 0;
    for (var i = 0; i < this.length; i++) {
        if (this.charCodeAt(i) > 255 || this.charCodeAt(i) < 0) len += 2; else len ++;
    }
    return len;
 }
 
//将字符串拆成字符，并存到数组中
String.prototype.strToChars = function(){
   var chars = new Array();
   for (var i = 0; i < this.length; i++){
       chars[i] = [this.substr(i, 1), this.isCHS(i)];
   }
   String.prototype.charsArray = chars;
   return chars;
}
//判断某个字符是否是汉字
String.prototype.isCHS = function(i){
   if (this.charCodeAt(i) > 255 || this.charCodeAt(i) < 0) 
       return true;
   else
       return false;
}
//截取字符串（从start字节到end字节）
String.prototype.subCHString = function(start, end){
   var len = 0;
   var str = "";
   this.strToChars();