text: //Calling the function
  document.addEventListener('DOMContentLoaded', start)
  
  function start() {
    //Binding visible
    var feeling = document.getElementById('feeling')
    feeling.addEventListener('click', handleVisibilityClick);
  
    //Binding options
    var options = document.getElementById('options')
    options.addEventListener('click', handleVisibilityClick);
  
    //Binding value
    var value = document.getElementById('value')
    value.addEventListener('click',handleVisibilityClick)
  
    //Binding operation
    var operators = document.getElementById('operators')
    operators.addEventListener('click',handleVisibilityClick)
  }
  
  
  
  // Event Handler by passing in event objects
  function handleVisibilityClick(e) {
    var items = document.getElementById(e.target.id + "-items");
  
    if (items.classList.contains("visible")) {
      items.classList.remove("visible")
      items.classList.add("invisible");
    } else {
      items.classList.remove("invisible")
      items.classList.add("visible");
    }
  }
  