How to use the pouchdb-merge.compactTree function in pouchdb-merge

function afterPutDoc(e) {
      var revsToDelete = docInfo.stemmedRevs || [];

      if (isUpdate && api.auto_compaction) {
        revsToDelete = revsToDelete.concat(compactTree(docInfo.metadata));
      }

      if (revsToDelete && revsToDelete.length) {
        compactRevs(revsToDelete, docInfo.metadata.id, txn);
      }

      metadata.seq = e.target.result;
      // Current _rev is calculated from _rev_tree on read
      // delete metadata.rev;
      var metadataToStore = encodeMetadata(metadata, winningRev,
        winningRevIsDeleted);
      var metaDataReq = docStore.put(metadataToStore);
      metaDataReq.onsuccess = afterPutMetadata;
    }

fetchedDocs.forEach(function (metadata, docId) {
        revsMap.set(docId, pouchdbMerge.compactTree(metadata));
      });
      compact(revsMap, callback);

fetchedDocs.forEach(function (metadata, docId) {
        revsMap.set(docId, compactTree(metadata));
      });
      compact(revsMap, callback);

function dataWritten(tx, seq) {
      var id = docInfo.metadata.id;

      var revsToCompact = docInfo.stemmedRevs || [];
      if (isUpdate && api.auto_compaction) {
        revsToCompact = compactTree(docInfo.metadata).concat(revsToCompact);
      }
      if (revsToCompact.length) {
        compactRevs(revsToCompact, id, tx);
      }

      docInfo.metadata.seq = seq;
      var rev = docInfo.metadata.rev;
      delete docInfo.metadata.rev;

      var sql = isUpdate ?
      'UPDATE ' + DOC_STORE +
      ' SET json=?, max_seq=?, winningseq=' +
      '(SELECT seq FROM ' + BY_SEQ_STORE +
      ' WHERE doc_id=' + DOC_STORE + '.id AND rev=?) WHERE id=?'
        : 'INSERT INTO ' + DOC_STORE +
      ' (id, winningseq, max_seq, json) VALUES (?,?,?,?);';

fetchedDocs.forEach(function (metadata, docId) {
        revsMap.set(docId, compactTree(metadata))
      })
      compact(revsMap, callback)

fetchedDocs.forEach(function (metadata, docId) {
        revsMap.set(docId, compactTree(metadata));
      });
      compact(revsMap, callback);