JavaScript - unable to select row from reactable table from checkbox

I have a checkbox on every row on my reactable table, which when clicked using a function called _onSelectARow should return all the data on that row, whilst the function fires, I am not getting the data on that, which is what I want to pass on to another redux function. My function is as follows:

 _onSelectARow = (index) => {
    return(event) => {
                       let selectrow = this.state.data.MyTableData.slice();

    if(event.target.checked){
         if(selectrow.indexof(index)==-1){
             selectrow.push(index);
             }
         }
    else{
          let found = selectrow.indexof(index);
          if(found >-1){
            selectrow.splice(found,1);
          }
        }
    this.setState({selectrow:selectrow});

Index is passed in on the row of the checkbox by {this._onSelectARow(index)}, and is set when data.map(row,index) is called binding the rows to the table.

The problem I am getting when the function is called, I am not the data of the row, but merely an index, and I cannot see why.

Is someone able to point out where the problem is and how I can fix it, please?

Thanks