sharepoint online – Hide / Show column based on another column choice

As you have mentioned, You need to show the Computer Issue if the Computer is selected, but the above code will show it only if it was not equal to != Computer.

So, you just need to swap it from show to hide if it’s not equal to Computer as below

<script type="text/javascript">
$(document).ready(function(){
   $('nobr:contains("Computer Issue")').closest('tr').hide();  
    //Show/hide columns based on Drop Down Selection 
   $("select(title='Subject')").change(function() {
 if ($("select(title='Subject')").val() != "Computer") 
   {
     $('nobr:contains("Computer Issue")').closest('tr').hide();
   } 
 else 
   {
     $('nobr:contains("Computer Issue")').closest('tr').show();
   }
   });
});
</script>

or, just change != to == as below

<script type="text/javascript">
    $(document).ready(function(){
       $('nobr:contains("Computer Issue")').closest('tr').hide();  
        //Show/hide columns based on Drop Down Selection 
       $("select(title='Subject')").change(function() {
     if ($("select(title='Subject')").val() == "Computer") 
       {
         $('nobr:contains("Computer Issue")').closest('tr').show();
       } 
     else 
       {
         $('nobr:contains("Computer Issue")').closest('tr').hide();
       }
       });
    });
    </script>

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