How to get randomised array element value on click in react?

board array contains 4 numbers, one of them will be randomly changed to the number 1, i need to get the value of that number on click. There are 4 buttons for each board numbers.

class GameContainer extends React.Component {
  state = {
    board: [0, 0, 0, 0]
  };

  generateBoard = () => {
    const newBoard = this.state.board;
    const random = Math.floor(Math.random() * 4);
    newBoard[random] = 1;
    return newBoard;
  };
  findWinner = () => {

  };

  componentWillMount = () => {
    const board = this.generateBoard();
    console.log("BOARD:", board);
    this.props.createBoard(board);
    console.log("Board created");
  };

  onClick = event => {
    console.log("Click received!", event.target.id);
    this.findWinner();
  };