JS/TS：二维字符串数组突然变得未定义时出错

Question

I'm making a Connect 4 game for a Discord.js application. I'm keeping the game board as a 2D array of strings and initializing it like so:

var board:string[][] = new Array<Array<string>>();

function resetBoard():void {
  for(let i=0; i<numRows; i++){
    board[i] = new Array<string>();
    for(let j=0; j<cols; j++){
      board[i].push(" ");
    }
  }
}

However, when I try to access a part of the board, it throws an error "cannot read property '0' of undefined".

function whatsAtPos(row, col){
  return board[row][col];
}

All of the functions are in the same file, and the board[][] is a global variable. I've tried everything up my sleeve to fix it and I have no idea what's going on.

Answer 1

i suggest you to:

• verify you called resetBoard() before you called whatsAtPos
• validate that while reseting board 'numRows', 'cols' that you used will be const or not change before calling
• add validation: to function whatsAtPos arguments about types, and during the function validate value of row, col that will be in range of [0, numRows-1], [0, cols-1]