Unexpected "undefined" element in 2D array assignment

Question

Below is my full code. For some reason it fails when setting board[2][0] and I can't see why. I'm sure it's something simple though...

function randColor() {
    min = Math.ceil(0);
    max = colors.length;
    return colors[Math.floor(Math.random() * (max - min)) + min]; 
}

const colCount = 10;
const rowCount = 10;

var board = [[],[]];

const colors = ["#f00","#0f0","00f"];

class piece {
    constructor(value, color) {
        this.value = value;
        this.color = color;
    }
}

for (var x = 0; x < colCount; x++) {
    for (var y = 0; y < rowCount; y++) {
        var p = new piece('b',randColor());
        console.log("Setting board[" + x + "][" + y + "]");
        board[x][y] = p;
    }
}

Matt · Accepted Answer · 2017-09-11 17:10:08Z

1

It's failing because you are creating your board incorrectly. It fails at 2 because you have [[ ],[ ]]. It would fail at 1 if you had [[ ]]..and so on for 3 etc.

Also your row is your outer loop and columns are your inner loop. The following will do what you need.

function randColor() {
    min = Math.ceil(0);
    max = colors.length;
    return colors[Math.floor(Math.random() * (max - min)) + min]; 
}

const colCount = 10;
const rowCount = 10;

var board = [];

const colors = ["#f00","#0f0","00f"];

function piece(value, color) {
    this.value = value;
    this.color = color;
}

for (var x = 0; x < rowCount; x++) {
    board[x] = [];
    for (var y = 0; y < colCount; y++) {
        var p = piece('b', randColor());
        console.log("Setting board[" + x + "][" + y + "]");
        board[x][y] = p;
    }
}

answered Sep 11, 2017 at 17:10

Matt

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