JavaScript: Soundex implementation

function soundex ( s_src )
{    
 var s_rez = "0000" ;
 var new_code, prev, idx
 
 a_codes = { "bfpv": 1, "cgjkqsxz":2, "dt": 3, "l": 4, "mn": 5, "r": 6 };
 
 s_src = s_src.toLowerCase().replace(/ /g,"")
 
 if ( s_src.length < 1) {
   return(s_rez);
 }
 
 s_rez = s_src.substr(0,1);
 prev = "0";
 
 for ( idx = 1 ; idx < s_src.length ; idx++) {
   new_code = "0";
   cur_char = s_src.substr(idx,1)
   
   for (s_code in a_codes)
      if (s_code.indexOf(cur_char) >= 0)
        { new_code = a_codes[ s_code ] ; break ; }

   if (new_code != prev && new_code != "0" )  {  
     s_rez += new_code;
   }
   
   prev = new_code;
  }
 
 s_rez = s_rez + "0000"
 
 return s_rez.substr(0,4);
}