getting total size of ArrayDataProvider

Question

I am using a knockout computed function to update a list with a filter based on inputs from user. This list has some predefined data, and when the filter is applied, I want to know the size of the resulting filtered list. I tried the following, but it doesn't print updated filtered data count.

this.dataprovider = ko.computed(function () {
  const filterRegEx = new RegExp(self.filter(), 'i');
  const filterCriterion = {
    op: '$or',
    criteria: [
      {
        op: '$regex',
        value: {
          name: filterRegEx,
        },
      },
      {
        op: '$regex',
        value: {
          dept: filterRegEx,
        },
      },
    ],
  };

  const arrayDataProvider = new ArrayDataProvider(self.data(), {
    keyAttributes: 'deptid',
  });

  const listDataProviderView = new ListDataProviderView(arrayDataProvider, {
    filterCriterion: filterCriterion,
  });

  listDataProviderView.getTotalSize().then(function (totalCount) {
    self.filteredCount('Total rows: ' + totalCount);
  });

  return listDataProviderView;
}, this);