Custom Sort Data table Column - first all numbers , String and null

I am trying to sort my data table based on custom requirement where I need to Sort first numbers , Second String and then null values at bottom of table. I have created data table where there are columns Age which has all three values. Whenever user clicks on Age , First number should be sorted then string and then null values at bottom. I have used method and override sort with $.fn.dataTable.ext.oSort

how Can I Sort first on numeric values then Text and then push null values to bottom.

I provided Link below for my Test Case with Data. Js Fiddle : Js Fiddle

Code :

$(document).ready(function() {
$.fn.dataTable.ext.errMode = 'none';    // stop pop-up alerts from datatable errors.
    
    
    $.fn.dataTable.ext.oSort['nullsort-asc']  = function(a,b) {
        console.log("asc val of:" + a + ":val of y:" + b);
          //return sortNumbersIgnoreText(a, b, Number.POSITIVE_INFINITY);
    if(a == "")
            return 1;
    if(b == "")
            return -1;
        return ((a < b) ? -1 : ((a > b) ? 1 : 0));
    };
    $.fn.dataTable.ext.oSort['nullsort-desc']  = function(a,b) {
    if(a == "")
            return 1;
        if(b == "")
            return -1;
        return ((a < b) ? 1 : ((a > b) ? -1 : 0));
    // return sortNumbersIgnoreText(a, b, Number.NEGATIVE_INFINITY) * -1;
    };

    $('#example').DataTable({
        //"aaSorting": [[3,'asc']],
      columnDefs: getColumnDef()
    });
} );


function getColumnDef(){
          return [
               
             { type: 'nullsort', targets: 3 },
             { type: 'nullsort', targets: 4}
            
            ];
}

Html:

<table id="example" class="display" cellspacing="0" width="100%">
  <thead>
    <tr>
      <th>Name</th>
      <th>Position</th>
      <th>Office</th>
      <th>Age</th>
      <th>Salary</th>
    </tr>
  </thead>
  <tfoot>
    <tr>
      <th>Name</th>
      <th>Position</th>
      <th>Office</th>
      <th>Age</th>
      <th>Salary</th>
    </tr>
  </tfoot>
  <tbody>
    <tr>
      <td>Tiger Nixon</td>
      <td>System Architect</td>
      <td>Edinburgh</td>
      <td></td>
      <td>$320,800</td>
    </tr>
     <tr>
      <td>James Nixon</td>
      <td>System Architect</td>
      <td>Edinburgh</td>
      <td></td>
      <td>$320,800</td>
    </tr>
    <tr>
      <td>Garrett Winters</td>
      <td>Accountant</td>
      <td>Tokyo</td>
      <td>63</td>
      <td></td>
    </tr>
    <tr>
      <td>Cedric Kelly</td>
      <td>Senior Javascript Developer</td>
      <td>Edinburgh</td>
      <td>22</td>
      <td>$433,060</td>
    </tr>
    <tr>
      <td>Airi Satou</td>
      <td>Accountant</td>
      <td>Tokyo</td>
      <td></td>
      <td>$162,700</td>
    </tr>
    <tr>
      <td>Brielle Williamson</td>
      <td>Integration Specialist</td>
      <td>New York</td>
      <td>61</td>
      <td></td>
    </tr>
    <tr>
      <td>Herrod Chandler</td>
      <td>Sales Assistant</td>
      <td>San Francisco</td>
      <td>59</td>
      <td>$137,500</td>
    </tr>
    <tr>
      <td>Rhona Davidson</td>
      <td>Integration Specialist</td>
      <td>Tokyo</td>
      <td>55</td>
      <td>$327,900</td>
    </tr>
    <tr>
      <td>Colleen Hurst</td>
      <td>Javascript Developer</td>
      <td>San Francisco</td>
      <td>39</td>
      <td>$205,500</td>
    </tr>
    <tr>
      <td>Sonya Frost</td>
      <td>Software Engineer</td>
      <td>Edinburgh</td>
      <td>A</td>
      <td>$103,600</td>
    </tr>
    <tr>
      <td>Jena Gaines</td>
      <td>Office Manager</td>
      <td>London</td>
      <td>30</td>
      <td>$90,560</td>
    </tr>
     <tr>
      <td>ADam Gaines</td>
      <td>Office Manager</td>
      <td>London</td>
      <td>Denis</td>
      <td>$90,560</td>
    </tr>
     <tr>
      <td>nancy Gaines</td>
      <td>Office Manager</td>
      <td>London</td>
      <td>zibra</td>
      <td>$90,560</td>
    </tr>
    <tr>
      <td>James Gaines</td>
      <td>Office Manager</td>
      <td>London</td>
      <td>capital</td>
      <td>$90,560</td>
    </tr>
  </tbody>
</table>

Solution

A couple comments first:

In the case (a == "" && b == "") you should return 0.
In JavaScript triple equals or === is used for a strict equal and often preferred.
"" is not equal to null. console.log('' == null); will output false.

Then for your question: You can test if something is a number with isNaN(). This count both let a = "123" and let a = 123 as numbers. You could also use typeof to check the data type.

Then I would do something kind of like this.

customSort = (a,b) => {
 const isNumA = !isNaN(a);//check if a is a number
 const isNumB = !isNaN(b);//check if b is a number

 if(!a && !b){return 0;}//if both are null return 0; don't need to change order
 else if(!a){return 1;}//if a is null and b isn't return 1
 else if(!b){return -1;} //if b is null and a isn't return -1
 else if(isNumA && isNumB){return Number(a) - Number(b);}//if they are both numbers do a number sort
 else if(isNumA){return -1;}//if a is a number and b isn't return 1
 else if(isNumB){return 1;}//if b is a number and a isn't return -1
 else {return (a).localeCompare(b);}//neither are number and neither are null, do a standard string sort
}

Then the sort is used like this:

const data = ['asdf', 'zxcv', null, '532', 234, null]; 
data.sort(customSort);

This is not fully tested but it works in my head and should be fairly close.