Pre-populating rows

Below example shows how cell renderers can be used to present the template values for empty rows. When a cell in the empty row is edited, the beforeChange callback fills the row with the template values.

var
  tpl = ['one', 'two', 'three'],
  data = [
    ['', 'Tesla', 'Nissan', 'Toyota', 'Honda'],
    ['2017', 10, 11, 12, 13],
    ['2018', 20, 11, 14, 13],
    ['2019', 30, 15, 12, 13]
  ],
  container = document.getElementById('example1'),
  hot1;

function isEmptyRow(instance, row) {
  var rowData = instance.countRows();

  for (var i = 0, ilen = rowData.length; i < ilen; i++) {
    if (rowData[i] !== null) {
      return false;
    }
  }

  return true;
}

function defaultValueRenderer(instance, td, row, col, prop, value, cellProperties) {
  var args = arguments;

  if (args[5] === null && isEmptyRow(instance, row)) {
    args[5] = tpl[col];
    td.style.color = '#999';
  }
  else {
    td.style.color = '';
  }
  Handsontable.renderers.TextRenderer.apply(this, args);
}

hot1 = new Handsontable(container, {
  startRows: 8,
  startCols: 5,
  minSpareRows: 1,
  contextMenu: true,
  cells: function (row, col, prop) {
    var cellProperties = {};

    cellProperties.renderer = defaultValueRenderer;

    return cellProperties;
  },
  beforeChange: function (changes) {
    var instance = hot1,
      ilen = changes.length,
      clen = instance.countCols(),
      rowColumnSeen = {},
      rowsToFill = {},
      i,
      c;

    for (i = 0; i < ilen; i++) {
      // if oldVal is empty
      if (changes[i][2] === null && changes[i][3] !== null) {
        if (isEmptyRow(instance, changes[i][0])) {
          // add this row/col combination to cache so it will not be overwritten by template
          rowColumnSeen[changes[i][0] + '/' + changes[i][1]] = true;
          rowsToFill[changes[i][0]] = true;
        }
      }
    }
    for (var r in rowsToFill) {
      if (rowsToFill.hasOwnProperty(r)) {
        for (c = 0; c < clen; c++) {
          // if it is not provided by user in this change set, take value from template
          if (!rowColumnSeen[r + '/' + c]) {
            changes.push([r, c, null, tpl[c]]);
          }
        }
      }
    }
  }
});

hot1.loadData(data);