Cannot add property xxxxxx, object is not extensible

[anandrikka]

I'm using fixed-data-table to render 1000 rows. I have a checkbox when clicked should show input boxes to edit the row.

checkboxSelect = (index, checkFlag) => {
  const {users} = this.state
  users[index]['selected'] = checkFlag // Getting Error Here
  this.setState({
    users,
  })
}

please help not sure what is the issue.