<button id="dialog-show-my-dialog" data-show-dialog-id="my-dialog" type="button" data-view-component="true" class="Button--secondary Button--medium Button">  <span class="Button-content">
    <span class="Button-label">Focus input</span>
  </span>
</button><tool-tip id="tooltip-762af789-b2d0-402d-b849-0ad0a1b4da5b" for="dialog-show-my-dialog" popover="manual" data-direction="s" data-type="description" data-view-component="true" class="sr-only position-absolute">This is a tooltip in an Overlay</tool-tip>
<dialog-helper>
  <dialog id="my-dialog" aria-modal="true" aria-labelledby="my-dialog-title" aria-describedby="my-dialog-description" data-view-component="true" class="Overlay Overlay-whenNarrow Overlay--size-medium Overlay--motion-scaleFade Overlay--disableScroll">
    <div data-view-component="true" class="Overlay-header">
      <div class="Overlay-headerContentWrap">
        <div class="Overlay-titleWrap">
          <h1 class="Overlay-title " id="my-dialog-title">
            Confirm focus
          </h1>
        </div>
        <div class="Overlay-actionWrap">
          <button data-close-dialog-id="my-dialog" aria-label="Close" type="button" data-view-component="true" class="close-button Overlay-closeButton"><svg aria-hidden="true" height="16" viewBox="0 0 16 16" version="1.1" width="16" data-view-component="true" class="octicon octicon-x">
              <path d="M3.72 3.72a.75.75 0 0 1 1.06 0L8 6.94l3.22-3.22a.749.749 0 0 1 1.275.326.749.749 0 0 1-.215.734L9.06 8l3.22 3.22a.749.749 0 0 1-.326 1.275.749.749 0 0 1-.734-.215L8 9.06l-3.22 3.22a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042L6.94 8 3.72 4.78a.75.75 0 0 1 0-1.06Z"></path>
            </svg></button>
        </div>
      </div>
    </div>
    <div data-view-component="true" class="Overlay-body">
      Are you sure you want to focus the input?
    </div>
  
    <div data-view-component="true" class="Overlay-footer Overlay-footer--alignEnd">
      <button id="yes-button" data-close-dialog-id="my-dialog" type="button" data-view-component="true" class="Button--secondary Button--medium Button">  <span class="Button-content">
          <span class="Button-label">Yes</span>
        </span>
      </button>
      <button data-close-dialog-id="my-dialog" type="button" data-view-component="true" class="Button--primary Button--medium Button">  <span class="Button-content">
          <span class="Button-label">Yes but in green</span>
        </span>
      </button>
    </div>
  </dialog></dialog-helper>
<label>
  An input
  <input type="text" id="input" autocomplete="off">
</label>
<script>
  document.querySelector('#my-dialog').addEventListener('close', function () {
    document.querySelector('#input').focus();
  });
</script>