suggestion.js

document.getElementsByClassName('custom-options')[0].addEventListener('click', function() {
  let lang = localStorage.getItem('lang');
  let greeting = document.getElementById('greetings');
  if (reg_name == 1) {
    let span = document.getElementById('spanName');
    switch(lang) {
      case "укр":
        greeting.innerHTML = "Ласкаво просимо до<br>Gradder" + "<span id='spanName'>, " + firstName + "</span>";
        span.style.opacity = "1";
        break;
      case "рус":
        greeting.innerHTML = "Добро пожаловать в<br>Gradder" + "<span id='spanName'>, " + firstName + "</span>";
        span.style.opacity = "1";
        break;
      case "eng":
        greeting.innerHTML = "Welcome to<br>Gradder" + "<span id='spanName'>, " + firstName + "</span>";
        span.style.opacity = "1";
        break;
    }
  } else if (reg_name == 0) {
    switch(lang) {
      case "укр":
        greeting.innerHTML = "Ласкаво просимо до<br>Gradder";
        break;
      case "рус":
        greeting.innerHTML = "Добро пожаловать в<br>Gradder";
        break;
      case "eng":
        greeting.innerHTML = "Welcome to<br>Gradder";
        break;
     }
  }
});