JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>www.bilisimogretmeni.com</title>
    <script language="javascript" type="text/javascript">
        function burcbul() {
            document.form1.gun.selectedIndex;
            document.form1.ay.selectedIndex;
            document.form1.burc.value;
            if (document.form1.ay.selectedIndex == 1 && document.form1.gun.selectedIndex <= 19) { document.form1.burc.value = "Oğlak"; }
            if (document.form1.ay.selectedIndex == 1 && document.form1.gun.selectedIndex >= 20) { document.form1.burc.value = "Kova"; }
            if (document.form1.ay.selectedIndex == 2 && document.form1.gun.selectedIndex <= 18) { document.form1.burc.value = "Kova"; }
            if (document.form1.ay.selectedIndex == 2 && document.form1.gun.selectedIndex >= 19) { document.form1.burc.value = "Balık"; }
            if (document.form1.ay.selectedIndex == 3 && document.form1.gun.selectedIndex <= 20) { document.form1.burc.value = "Balık"; }
            if (document.form1.ay.selectedIndex == 3 && document.form1.gun.selectedIndex >= 21) { document.form1.burc.value = "Koç"; }
            if (document.form1.ay.selectedIndex == 4 && document.form1.gun.selectedIndex <= 20) { document.form1.burc.value = "Koç"; }
            if (document.form1.ay.selectedIndex == 4 && document.form1.gun.selectedIndex >= 21) { document.form1.burc.value = "Boğa"; }
            if (document.form1.ay.selectedIndex == 5 && document.form1.gun.selectedIndex <= 20) { document.form1.burc.value = "Boğa"; }
            if (document.form1.ay.selectedIndex == 5 && document.form1.gun.selectedIndex >= 21) { document.form1.burc.value = "İkizler"; }
            if (document.form1.ay.selectedIndex == 6 && document.form1.gun.selectedIndex <= 20) { document.form1.burc.value = "İkizler"; }
            if (document.form1.ay.selectedIndex == 6 &&...