Código HTML:
<html> <head> <script language="JavaScript"> function currencyFormat(fld, milSep, decSep, e) { var sep = 0; var key = ''; var i = j = 0; var len = len2 = 0; var strCheck = '0123456789'; var aux = aux2 = ''; var whichCode = (window.Event) ? e.which : e.keyCode; if (whichCode == 13) return true; // Enter key = String.fromCharCode(whichCode); // Get key value from key code if (strCheck.indexOf(key) == -1) return false; // Not a valid key len = fld.value.length; for(i = 0; i < len; i++) if ((fld.value.charAt(i) != decSep)) break; aux = ''; for(; i < len; i++) if (strCheck.indexOf(fld.value.charAt(i))!=-1) aux += fld.value.charAt(i); aux += key; len = aux.length; if (len == 0) fld.value = ''; if (len == 1) fld.value = aux; if (len == 2){ if (aux>31) window.alert("El dia debe ser inferior a 31");//CAPULLO else fld.value = aux; } if (len > 2 && len < 5) { if (len == 4){ if (aux.substr(len - 2, len)>12) window.alert("El mes debe ser inferior a 12");//RECAPULLO, ES Q NO SABES DE FECHAS?? else fld.value = aux; } aux2 = ''; for (j = 0, i = len - 3; i >= 0; i--) { if (j == 2) { aux2 += milSep; j = 0; } aux2 += aux.charAt(i); j++; } fld.value = ''; len2 = aux2.length; for (i = len2 - 1; i >= 0; i--) fld.value += aux2.charAt(i); fld.value += decSep + aux.substr(len - 2, len); } if (len > 4 && len < 9) { aux2 = ''; for (j = 0, i = len - 3; i >= 0; i--) { if (j == 2 && i <= len -5) { aux2 += milSep; j = 0; } aux2 += aux.charAt(i); j++; } fld.value = ''; len2 = aux2.length; for (i = len2 - 1; i >= 0; i--) fld.value += aux2.charAt(i); fld.value += aux.substr(len - 2, len); } return false; } </script> </head> <body> <form> Introduzca un número: <input type="text" name="test" length="15" onKeyPress="return(currencyFormat(this,'/','/',event))"> </form> </body> </html>