2D Javascript数组TypeError

Question

[EDIT] Full application available at: http://bit.ly/1CGZzym

I'm receiving the error:

Uncaught TypeError: Cannot set property '0' of undefined

with the following code. I believe it is due to my not declaring the child array of the 2D array properly but I am really confused as to where I should be declaring this. Any ideas would be excellent.

// Create an array for the tiles we're about to draw
var tileArray = []

is declared out side of the function.

I assume it is because I am trying to create child elements within each [col] so I guess I need to declare each col number somewhere but nothing I attempt seems to be working.

function drawGrid()
        {

            // Draw diamond grid

            var col = 0;
            var row = 0;

            topTileX = (viewWidth/2);
            topTileY = 0;

            var nextX = 0;
            var nextY = 0;

            var getCols = 0;

            while (topTileX > -1)
            {

                tileArray[col][row] = new DiamondTile(topTileX, topTileY, tileWidth, true, col, row);
                tileArray[col][row].draw();

                while (tileArray[col][row].xPos + tileArray[col][row].tileWidth < (viewWidth) + tileWidth)
                {
                    col++;

                    nextX = tileArray[col-1][row].xPos + tileArray[col-1][row].tileWidth / 2;
                    nextY = tileArray[col-1][row].yPos + tileArray[col-1][row].tileHeight / 2;

                    tileArray[col][row] = new DiamondTile(nextX, nextY, tileWidth, true, col, row);
                    tileArray[col][row].draw();

                    if (col == getCols)
                            {
                                break;
                            }
                }

            row++;
            getCols = col;
            col = 0;

            topTileX = topTileX - tileWidth/2;
            topTileY = topTileY + tileHeight/2;

            }
        };

For the purpose of demonstration, the DiamondTile function is as follows:

function DiamondTile(xPos,yPos,width,interactive,myCol,myRow)
        {
            // Set x and y position for this sprite
            this.xPos = xPos;
            this.yPos = yPos;
            this.myRow = myRow;
            this.myCol = myCol;

            // Used for AI pathfinding
            this.isObstacle = false;
            this.isStart = false;
            this.isEnd = false;

            this.gValue = 0;
            this.hValue = 0;
            this.fCost = 0;

            this.tileWidth = width;
            this.tileHeight = this.tileWidth/2;

            var self = this;

            // Create sprite
            this.spriteObj = new PIXI.Sprite(grass);
            this.spriteObj.interactive = interactive;

            this.spriteObj.anchor = new PIXI.Point(0.5,0);

            this.spriteObj.hitArea = new PIXI.Polygon([
                new PIXI.Point(0,0),
                new PIXI.Point(100,50),
                new PIXI.Point(0,100),
                new PIXI.Point(-100,50)
                ]);

            this.spriteObj.mouseover = function()
            {
                if (self.spriteObj.tint == 0xFFFFFF)
                {
                self.spriteObj.tint = 0xA7E846;
                }

                text2.setText(self.myCol + "," + self.myRow + " Start: " + self.isStart);
            }
            this.spriteObj.mouseout = function()
            {
                if (self.spriteObj.tint == 0xA7E846)
                {
                self.spriteObj.tint = 0xFFFFFF;
                }
            }
            this.spriteObj.click = function()
            {
                if (startStage === true)
                {
                    startStage = false;
                    self.isStart = true;
                    self.spriteObj.tint = 0x1AFF00;
                    text.setText("Now select an end point");
                    endStage = true;
                    return true;
                }
                if (endStage === true)
                {
                    endStage = false;
                    self.isEnd = true;
                    self.spriteObj.tint = 0xFF0000;
                    text.setText("Now place some obstacles");
                    obsStage = true;
                    return true;
                }
                if (obsStage ===true)
                {
                    self.isObstacle = true;
                    self.spriteObj.tint = 0x3B3B3B;
                    text.setText("Press 'C' to calculate path");
                    return true;
                }

            }


        };

Answer 1

That is a multi-dimensional array and you have not initialized the first dimension array correctly. In the while loop you have to initialize the first dimension to be able to access a second dimension element with an index:

while (topTileX > -1)
{
    if (tileArray[col] == null)
        tileArray[col] = [];

    tileArray[col][row] = new DiamondTile(topTileX, topTileY, tileWidth, true, col, row);
    tileArray[col][row].draw();

    // omitted other code for brevity
}

Javascript arrays are dynamic and it's enough to initialize the first dimension array elements in this case. You don't have to initialize the individual items in the second dimension.

Update : here is a fiddle with working code http://jsfiddle.net/0qbq0fts/2/

In addition your semantics is wrong. By the book, the first dimension of a 2-dimensional array should be rows, and the second dimension should be columns.

Answer 2

You have to explicit create the elements representing the second dimension, eg:

function make2DArray(rows, cols) {
    var r = Array(rows);
    for (var i = 0; i < rows; ++i) {
        r[i] = Array(cols);
    }
    return r;
}

If you don't know in advance how many columns, just use this:

function make2DArray(rows) {
    var r = Array(rows);
    for (var i = 0; i < rows; ++i) {
        r[i] = [];
    }
    return r;
}

The individual rows can each have independent lengths, and will grow as you add values to them.

Similarly, if you just need to add a new (empty) row, you can just do:

tileArray.push([]);

Answer 3

This should probably me a comment, but SO has crashed on my side. JavaScript might be throwing an exception on your stated line, but the problem may be with the 'DiamondTile' function.