// exemplo para utilização da máscara, para CPF e CNPJ
///onBlur="formatarCPFCNPJ('txt_nr_cnpj',event);" 
////onKeyPress="formatarCPFCNPJ('txt_nr_cnpj',event);"

function formatarCPFCNPJ(campo,teclapres) {
 var tammax = 14;
 var tecla = teclapres.keyCode;
  //alert(tecla);
 vr = event.srcElement.value;
 vr = vr.replace( "/", "" );
 vr = vr.replace( "/", "" );
 vr = vr.replace( ",", "" );
 vr = vr.replace( ".", "" );
 vr = vr.replace( ".", "" );
 vr = vr.replace( ".", "" );
 vr = vr.replace( ".", "" );
 vr = vr.replace( "-", "" );
 vr = vr.replace( "-", "" );
 vr = vr.replace( "-", "" );
 vr = vr.replace( "-", "" );
 vr = vr.replace( "-", "" );
 tam = vr.length;

 if (tam < tammax && tecla != 8){ tam = vr.length + 1 ; }

 if (tecla == 8 ){ tam = tam - 1 ; }

 if (tecla == 0 && tam<=12){
 	tam --;
 }
//alert(tam);
 if ( tecla == 8 || tecla >= 48 && tecla <= 57 || tecla >= 96 && tecla <= 105 || tecla == 0 ){
  if ( tam <= 2 ){ 
    event.srcElement.value = vr ; }
   if ( (tam > 2) && (tam <= 5) ){
    event.srcElement.value = vr.substr( 0, tam - 2 ) + '-' + vr.substr( tam - 2, tam ) ; }
   if ( (tam >= 6) && (tam <= 8) ){
    event.srcElement.value = vr.substr( 0, tam - 5 ) + '.' + vr.substr( tam - 5, 3 ) + '-' + vr.substr( tam - 2, tam ) ; }
   if ( (tam >= 9) && (tam <= 11) ){
    event.srcElement.value = vr.substr( 0, tam - 8 ) + '.' + vr.substr( tam - 8, 3 ) + '.' + vr.substr( tam - 5, 3 ) + '-' + vr.substr( tam - 2, tam ) ; }
   if ( (tam >= 12) && (tam <= 14) ){
    event.srcElement.value = vr.substr( 0, tam - 12 ) + '.' + vr.substr( tam - 12, 3 ) + '.' + vr.substr( tam - 9, 3 ) + '/' + vr.substr( tam - 6, 4 ) + '-' + vr.substr( tam - 2, tam ) ; }
 }  
}