_token.html.erb

<script type="text/javascript">
  $('#btn-token').on('click',function() {
    var token = '<%= @user.user.token %>';

    var mask = document.createElement('div');
    mask.className = 'mask';
    mask.id = 'token-mask';

    mask.innerHTML = '\
      <div class="modal-dialog" id="token-popup">\
        <div class="modal-content">\
          <div class="modal-header">\
            <button type="button" class="close" id="close-btn">&times;</button>\
            <h4 class="modal-title">Access Token</h4>\
          </div>\
          <div class="modal-body">\
            <p><span class="token form-control text-center"></span></p>\
          </div>\
          <div class="modal-footer">\
            <button type="button" class="btn btn-default" id="copy-btn">Copy</button>\
          </div>\
        </div>\
      </div>\
    ';

    $('body').append(mask);
    $('#token-mask').fadeIn(200, function(){
      $('#token-popup .token').text(token);
      $('#token-popup .modal-content').animate({marginTop: '30px', opacity: '1'}, 300);
      $('#token-mask').on('click', closePopup);
      $('#token-popup #copy-btn').on('click', copyToken);
    });
  });

  function copyToken(){
    var temp = $('<input>');
    $("body").append(temp);
    temp.val($('#token-popup .token').text()).select();
    document.execCommand('copy');
    temp.remove();

    $('#token-popup #copy-btn').text('Copied').attr('disabled', 'true');
  };

  function closePopup(e){
    var tokenPopup = document.querySelector('#token-popup .modal-content');
    if (tokenPopup === e.target || tokenPopup.contains(e.target) && e.target.id !== 'close-btn'){
      return;
    };

    $('#token-popup .modal-content').animate({marginTop: '0', opacity: '0'}, 300, function(){
      $(this).remove();
      $('#token-mask').fadeOut(200, function(){
        $(this).remove();
      });
    });
  };
</script>

<style type="text/css">
  .mask{
    display: none;
    z-index: 10000;
    position: fixed;
    height: 100%;
    width: 100%;
    top: 0;
    background-color: rgba(0, 0, 0, 0.7);
  }

  .modal-dialog{
    margin-top: 0;
  }
  
  .modal-content{
    opacity: 0;
  }

  .token{
    font-weight: bold;
  }
</style>