How to fix two rows at top when sorting a google visualization table?

Question

I have two rows in a google visualization table that I want to keep fixed at the top after a sort and then draw the table again. I'm using:

var data = new google.visualization.DataTable();
var table1 = new google.visualization.Table(document.getElementById('my_div'));
var ascendOrDescend = true;
...
data.sort({column: colIndex, desc: ascendOrDescend});
ascendOrDescend = !ascendOrDescend;
table1.draw(data, options);

Is there a way to fix those two rows or after the sort force them back to the top?

Answer 1

in order to fix a row at a certain position within the sort,
you need to manually control the sort order.

to control manually, set the following option when drawing the table.

var options = {
  sort: 'event'
};

the table's sort event will provide the column and direction requested by the user
you can pass the column and direction to data table method getSortedRows
which will return an array of row indexes that meet the sort criteria

// table sort event
google.visualization.events.addListener(table, 'sort', function (sender) {
  // get sorted rows indexes
  var sortIndexes = data.getSortedRows({column: sender.column, desc: !sender.ascending});

we can manipulate the array of row indexes by moving the row indexes we want at the top
and create a data view and use the setRows method to provide the order in which the data view should appear

var view = new google.visualization.DataView(data);
view.setRows(sortIndexes);

in order for the table to display the sort direction arrow above the correct column we set the following table options

options.sortAscending = sender.ascending;
options.sortColumn = sender.column;

then draw the table using the newly created data view

see following working snippet,
the rows for 'Michael' and 'Elisa' will remain at the top after each sort

google.charts.load('current', {
  packages: ['corechart', 'table']
}).then(function () {
  var data = google.visualization.arrayToDataTable([
    ['Name', 'RoolNumber', 'Gender', 'Age', 'Donuts eaten'],
    ['Michael', 1, 'Male', 12, 5],
    ['Elisa', 2, 'Female', 20, 7],
    ['Robert', 3, 'Male', 7, 3],
    ['John', 4, 'Male', 54, 2],
    ['Jessica', 5, 'Female', 22, 6],
    ['Aaron', 6, 'Male', 3, 1],
    ['Margareth', 7, 'Female', 42, 8],
    ['Miranda', 8, 'Female', 33, 6]
  ]);

  var table = new google.visualization.Table(document.getElementById('table'));
  var options = {
    sort: 'event'
  };

  // table sort event
  google.visualization.events.addListener(table, 'sort', function (sender) {
    // get sorted rows indexes
    var sortIndexes = data.getSortedRows({column: sender.column, desc: !sender.ascending});

    // move values to top
    moveToTop(sender, sortIndexes, 'Elisa');
    moveToTop(sender, sortIndexes, 'Michael');

    // set table sort arrow
    options.sortAscending = sender.ascending;
    options.sortColumn = sender.column;

    // build table view with custom sort
    var view = new google.visualization.DataView(data);
    view.setRows(sortIndexes);

    // draw table with view
    table.draw(view, options);
  });

  // move value to top of sort
  function moveToTop(sender, sortIndexes, value) {
    // find value in current sort
    var fixedRows = data.getFilteredRows([{
      column: 0,
      value: value
    }]);
    if (fixedRows.length > 0) {
      // move value to top
      sortIndexes.splice(sortIndexes.indexOf(fixedRows[0]), 1);
      sortIndexes.unshift(fixedRows[0]);
    }
  }

  // first draw
  table.draw(data, options);
});

<script src="https://www.gstatic.com/charts/loader.js"></script>
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