Function findPrevFrag

06.Router/basic/js/vue.js:4532–4544

* Helper to find the previous element that is a fragment * anchor. This is necessary because a destroyed frag's * element could still be lingering in the DOM before its * leaving transition finishes, but its inserted flag * should have been set to false so we can skip them. * * If

(frag, anchor, id)

   */

  function findPrevFrag(frag, anchor, id) {
    var el = frag.node.previousSibling;
    /* istanbul ignore if */
    if (!el) return;
    frag = el.__v_frag;
    while ((!frag || frag.forId !== id || !frag.inserted) && el !== anchor) {
      el = el.previousSibling;
      /* istanbul ignore if */
      if (!el) return;
      frag = el.__v_frag;
    }
    return frag;
  }

  /**
   * Find a vm from a fragment.