code: function findEntriesByCheck(groupParent, check, key, value) {
      // If the groupParent object is a Group, use it as the only search group,
      // otherwise just take the children groups (groupParent is probably an
      // Archive instance):
      let groups = groupParent.getEntries ? [groupParent] : groupParent.getGroups();
      return instanceSearching.findEntriesByCheck(groups, function(entry) {
          var itemValue;
          switch (check) {
              case "property": {
                  itemValue = entry.getProperty(key) || "";
                  break;
              }
              case "meta": {
                  itemValue = entry.getMeta(key) || "";
                  break;
              }
              case "id": {
                  return value === entry.id;
              }
              default:
                  throw new Error(`Unknown check instruction: ${check}`);
          }
          if (value instanceof RegExp) {
              return value.test(itemValue);
          } else {
              return itemValue.indexOf(value) >= 0;
          }
      });
  }
docs: Find entries by searching properties/meta
  When used within a group, that group's entries are also searched'
  @param {Archive|Group} groupParent The target archive or group
  @param {string} check Information to check (id/property/meta)
  @param {string} key The key (property/meta-value) to search with (not needed for check=id)
  @param {RegExp|string} value The value to search for
  @returns {Array.<Entry>} An array of found entries
  @private
  @static
  @memberof EntryCollection