How to dynamically align ag-grid-angular headers

I have an ag-grid with angular 6 and dynamically appended columns and data. Now I want to align the headers (parent and child in case of multiple headers) dynamically. Like the first column header should be left aligned and other headers should be center aligned.

I tried to set cellStyle and other options I found but none of them work

I tried to implement it like this:

  let headerItem = {
    headerName: name,
    children: [
      {
        headerName: name,
        field: 'col' + i + '.value',
        hide: isHidden,
        pinned: pinned,
        cellStyle: function (params) {
          try {
            return {text-align : 'center'};
          } catch (e) {
            return null;
          }
        }
      }
    ],
    cellStyle: function (params) {
          try {
            return {text-align : 'center'};
          } catch (e) {
            return null;
          }
        }
  }

Please guide me how to make it work...