form test

HTML

<div class="search-container">
  <form class="search-form">
    <input class="search-form__input" type="text" placeholder="Search...">
    <button class="search-form__button" type="submit">button</button>
  </form>
</div>

JavaScript

const searchForm = document.querySelector('.search-form');
let globalVar;

function test() {
  globalVar = searchForm.value;
}

searchForm.addEventListener('submit', test);