How to use and purpose of localstorage in javascript

• Show modal using localStorage in javascript

  <!-- set localStorage item with key openModal and value #addEventModal -->
  <!-- index.html -->
  <a id="addEventBtn" href="main.html"> Add Event </a>
  
  <script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
  <script>
      $(document).ready(function(){
          $('#addEventBtn').on('click', function(e){
              e.preventDefault();
              localStorage.setItem('openModal', '#addEventModal');
              let href = e.target.href;
              window.location.replace(href);
          });
      })
  </script>
  <!-- Get the localStorage with getItem method and show modal if it is not null and after that remove item from storage -->
  <!-- main.html -->
  <div class="modal" id="addEventModal">
     <div class="modal-dialog ">
         <div class="modal-content">
             <div class="modal-header">
                <h4 class="modal-title">Modal title</h4>
                 <button type="button" class="close" data-dismiss="modal">&times;</button>
             </div>
            <div class="modal-body">
          <p>Modal body text goes here.</p>
            </div>
             <div class="modal-footer">
                <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
                 <button type="button" class="btn btn-primary">Save changes</button>
            </div>
         </div>
    </div>
  </div>
  <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" integrity="sha384-TX8t27EcRE3e/ihU7zmQxVncDAy5uIKz4rEkgIXeMed4M0jlfIDPvg6uqKI2xXr2" crossorigin="anonymous">
  <script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
  <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js" integrity="sha384-ho+j7jyWK8fNQe+A12Hb8AhRq26LrZ/JpcUGGOn+Y7RsweNrtN/tE3MoK7ZeZDyx" crossorigin="anonymous"></script>
  <script>
  var modalId = localStorage.getItem('openModal');
  if(modalId != null){
      $(modalId).modal("show"); //use modal with id addEventModal
      localStorage.removeItem('openModal');
  }
  </script>
  

  It will help you to set the localStorage with modal id in one page using javascript and will show modal to another page after the redirection and remove the item after showing the modal so that on next visit modal did not show. 

  setItem in one page and show modal, remove localStorage item using removeItem after showing the modal

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