JSFiddle - React, Tailwind, and code Playground

HTML

<input type="radio" name="radio" value="kai" checked> KAI
<input type="radio" name="radio" value="raillink"> RAILINK

<input type="submit" id="search-button" value="Cari tiket KAI">

JavaScript

$('input[name=radio]').click(function(){
    var nilai = $(this).val();
    
    $('#search-button').val("Cari tiket " + nilai.toUpperCase());
 });
 
$('#search-button').click(function() {
	var a = $('input[name=radio]:checked');
  console.log(a, a.val());
	if (a.val() === "kai") {
  	alert("kai");
  } else {
    alert("railink")
  }
})