An array of arrays confusion

Question

I'm trying to display the levels I'll have using this code...

levelArray[0] = ["player", "empty", "empty", "empty", "wall", "wall", "empty",
    "empty", "wall", "wall", "empty", "empty", "empty","empty",
    "empty", "empty", "empty", "wall", "empty", "wall", "wall",
    "wall", "wall", "empty", "wall", "empty", "wall", "empty",
    "box", "wall", "empty", "wall", "empty", "empty", "empty",
    "empty", "empty", "empty", "wall", "wall", "wall", "empty",
    "wall", "wall", "empty", "empty", "ghost", "wall","ghost"];

for(var i = 0; i < edge; i++)
{
    for(var j = 0; j < edge; j++)
    {
        switch(levelArray[i])
        {
            case "empty":   // empty location
                ctx.drawImage(emptyTile, currentX, currentY);
                break;
            case "wall":    // wall block
                ctx.drawImage(wallTile, currentX, currentY);
                break;
            case "box":     // box block
                ctx.drawImage(boxTile, currentX, currentY);
                break;
            case "ghost":   // enemy sprite
                ctx.drawImage(ghostTile, currentX, currentY);
                break;
            case "player":  // player sprite
                ctx.drawImage(playerTile, currentX, currentY);
                break;
        }
        currentX += elementEdge;
    }
    currentY += elementEdge;
}

however I receive an error on the switch line "Uncaught TypeError: Cannot read property '0' of undefined" and I don't really understand it.

Edit: edge is defined previously like this

edge = Math.sqrt(levelArray.length)

Where's edge defined? And you're using it for both for loops? Shouldn't it be levelArray.length and levelArray[i].length? — somedev
– somedev, Commented Aug 13, 2013 at 14:44

bfavaretto · Accepted Answer · 2013-08-13 17:08:38Z

0

You're not using the inner loop. I believe you want this instead:

switch(levelArray[i][j])

In your source code, that snippet is inside a setupCanvas function, with takes levelArray as an argument. Since you're not passing anything when you call setupCanvas, it's considered undefined. Hence the errors you're getting.

edited Aug 13, 2013 at 17:08

answered Aug 13, 2013 at 14:44

bfavaretto

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7 Comments

bfavaretto Over a year ago

Make sure edge is defined, and levelArray is properly initialized (var levelArray = []) somewhere

Cody Over a year ago

Edge is defined and levelArray is properly initialised

bfavaretto Over a year ago

@Cody Could you setup a jsfiddle that reproduces the problem?

bfavaretto Over a year ago

@Cody That's too much code for me to debug right now. But I ran it, and didn't get any errors.

Cody Over a year ago

Click on the output, I just threw it all in so it'd be a proper representation of what I have

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gred · Accepted Answer · 2013-08-13 14:45:44Z

0

Try to access your array of levelArray like this:

switch(levelArray[0][i])

, because this levelArray[i] will return array in case i=0 for sure and other cases of i if you have placed more arrays!

answered Aug 13, 2013 at 14:45

gred

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1 Comment

gred Over a year ago

What is the value of edge? Try instead of edge, 48 and remove one of the two for loops.

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