\uXXXX encode

   function stringEncode(preescape){
      var escaped="";
      var i=0;
      for(i=0;i<preescape.length;i++){
         escaped=escaped+encodeCharx(preescape.charAt(i));
      }
      return escaped;
   }
   function encodeCharx(original){
      var hex=new Array('0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f');
      var thechar=original.charCodeAt(0);
      if(thechar>127) {
         var c=thechar;
         var a4=c%16;
         c=Math.floor(c/16);
         var a3=c%16;
         c=Math.floor(c/16);
         var a2=c%16;
         c=Math.floor(c/16);
         var a1=c%16;
         return "\\u"+hex[a1]+hex[a2]+hex[a3]+hex[a4]+"";
      } else
         return original;
   }
   stringEncode('КириллицаAnySymbols()"[]'); // -> \u041a\u0438\u0440\u0438\u043b\u043b\u0438\u0446\u0430AnySymbols()"[]