JavaScript calculates the checksum including 10 as a solution

[Janechen88]

Hello dear community,

I have a problem and I don't know exactly how to solve it.
I have a code that calculates the checksum of a number and then outputs it.

I would now have to adapt the code so that the number "10" can also come out as a solution.
That means the checksum of 91 should be 10 and not 1 (so the number must be >10 so that it calculates the checksum)

how can I add an if condition or something else to my code that I achieve this result.

I would be really grateful for suggestions and solutions 🙂

jQuery( function( $ ) {
 
 
  $("input[name='wpcf-geburtdatumzahl1']").change(quersumme);


  function quersumme() {
       
   
        var tmp = $("input[name='wpcf-geburtdatumzahl1']").val().split('');
        var quer = 0;
   
        for (var i=0; i < tmp.length; i++) {
          quer += Number(tmp[i]);
        }
       
   
        var round2 = quer.toString().split('');
        var round2_res = 0;
        for (var i=0; i < round2.length; i++) {
          round2_res += Number(round2[i]);
        }


        $("input[name='wpcf-loesungszahl01']").val(round2_res);
   
         
}
   
} );