JSFiddle - React, Tailwind, and code Playground

by Peter Aad

HTML

<select id="gameid">
    <option value="1">1</option>
     <option value="2">2</option>
     <option value="3">3</option>
     <option value="4">4</option>
</select>

<select id="netid">
    <option value="1">1</option>
     <option value="2">2</option>
     <option value="3">3</option>
     <option value="4">4</option>
</select>

<select id="camp_id">
</select>

JavaScript

var a = $("#gameid").val(),
 b = $("#netid").val(),
 c;

$("#gameid, #netid").change(function(){
   a = $("#gameid").val();  
   b = $("#netid").val();  
   c = parseInt(a)+parseInt(b); 
   $("#camp_id").empty();
        
   for (var i = 1; i<=999; i++){
    $("#camp_id").append("<option value='"+(c+i)+"'>"+(c+i)+"</option>");
   }   
});