     </button>
              <span> | </span>
              <button
                id="button-show-v6"
                onclick="showCodeVersion('v6')"
                type="button"
                class="btn btn-secondary btn-sm"
              >
                d3 v6
              </button>
            </div>

            <!-- ========= show html code ============== -->
            <aside
              style="position: -webkit-sticky; position: sticky; top: 120px"
            >
              &larr; Edit me