String.prototype.trim = function() {
      return this.replace(/(^\s*)|(\s*$)|($\s*)/g, "");
   }

   String.prototype.isid = function() {
      if (this.search(/[^A-Za-z0-9_-]/) == -1)
         return true;
      else 
         return false;
   }

   String.prototype.isalpha = function() {
      if (this.search(/[^A-Za-z]/) == -1)
         return true;
      else
         return false;
   }

   String.prototype.isnumber = function() {
      if (this.search(/[^0-9]/) == -1)
         return true;
      else
         return false;
   }

   String.prototype.isemail = function() {
      var flag, md, pd, i;
      var str;

      if ( (md = this.indexOf("@")) < 0 )
         return false;
      else if ( md == 0 )
         return false;
      else if (this.substring(0, md).search(/[^.A-Za-z0-9_-]/) != -1)
         return false;
      else if ( (pd = this.indexOf(".")) < 0 )
         return false;
      else if ( (pd + 1 )== this.length || (pd - 1) == md )
         return false;
      else if (this.substring(md+1, this.length).search(/[^.A-Za-z0-9_-]/) != -1)
         return false;
      else
         return true;
   }

   String.prototype.korlen = function() {
      var temp;
      var set = 0;
      var mycount = 0;
      
      for( k = 0 ; k < this.length ; k++ ){
         temp = this.charAt(k);
      
         if( escape(temp).length > 4 ) {
            mycount += 2; 
         }
         else mycount++;
      }

      return mycount;
   }

    String.prototype.isssn = function() {
    
        var first  = new Array(6);
        var second = new Array(7);
        var total = 0;
        var tmp = 0;
        
        if ( this.length != 13 )
            return false;
        else {
            for ( i = 1 ; i < 7 ; i++ )
                first[i] = this.substring(i - 1, i);
        
            for ( i = 1 ; i < 8 ; i++ )
                second[i] = this.substring(6 + i - 1, i + 6);
        
            for ( i = 1 ; i < 7 ; i++ ) {
                if ( i < 3 )
                    tmp = Number( second[i] ) * ( i + 7 );
                else if ( i >= 3 )
                    tmp = Number( second[i] ) * ( ( i + 9 ) % 10 );
        
                total = total + Number( first[i] ) * ( i + 1 ) + tmp;
            }
        
            if ( Number( second[7] ) != ((11 - ( total % 11 ) ) % 10 ) ) 
                return false;
        }
        return true;
    }