compare(rows_1, rows_2) {
  rows_1.forEach(row_1 => {
    rows_2.forEach(row_2 => {
      row_1['checked'] = row_1.id === row_2.sub.id;
    });
  });
}

rows_1 = [ {id: '1', title: '...'}, {id: '2', title: '...'}, ];
rows_2 = [ {sub: {id: '1', title: '...'}}, {sub: {id: '2', title: '...'}} ];

[ { id: 9, title: '...', checked: false },
  { id: 8, title: '...', checked: false },
  { id: 7, title: '...', checked: false },
  { id: 6, title: '...', checked: false },
  { id: 5, title: '...', checked: false },
  { id: 4, title: '...', checked: false },
  { id: 3, title: '...', checked: false },
  { id: 2, title: '...', checked: false },
  { id: 1, title: '...', checked: true } ]

[ { id: 9, title: '...', checked: false },
  { id: 8, title: '...', checked: false },
  { id: 7, title: '...', checked: false },
  { id: 6, title: '...', checked: false },
  { id: 5, title: '...', checked: true },
  { id: 4, title: '...', checked: true },
  { id: 3, title: '...', checked: true },
  { id: 2, title: '...', checked: true },
  { id: 1, title: '...', checked: true } ]