JSFiddle - React, Tailwind, and code Playground

HTML

<form id="calc-form" method="POST" action="javascript:void(null);" onsubmit="calc()" class="calc-form">
  .....
  <div class="calc-form-options flex">
    <div class="select">
      <p>Выберите опцию</p>
      <select name="select[]" class="calc-form-input">
        <option class="calc-form-option" value="Шлифзерно"><span>Шлифзерно</span></option>
        <option class="calc-form-option" value="Шлифпорошки"><span>Шлифпорошки</span></option>
        <option class="calc-form-option" value="Электрокорунд"><span>Электрокорунд</span></option>
      </select>
    </div>
    <div class="select">
      <p>Введите количество</p>
      <input class="calc-form-input" name="select2[]" placeholder="Введите число">
    </div>                            
    <div class="select">
      <p>Выберите опцию</p>
      <select name="select3[]" class="calc-form-input">
        <option class="calc-form-option" value="Шлифзерно"><span>Шлифзерно</span></option>
        <option class="calc-form-option" value="Шлифпорошки"><span>Шлифпорошки</span></option>
        <option class="calc-form-option" value="Электрокорунд"><span>Электрокорунд</span></option>
      </select>
    </div>
  </div>   
  <div class="calc-form-options-add flex"> 
  </div> 
  ......
</form>

JavaScript

$('form').on('change', function(){
	var data = $('#calc-form').serialize();
  console.log(data)
})