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Asked: 2026-06-03T05:46:13+00:00

I’m using a A* pathfinding script in a simple JavaScript. I broke my game

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I’m using a A* pathfinding script in a simple JavaScript. I broke my game down to a SSCCE. Anyway, my game is 15 columns across and 10 rows down.

The pathfinding works until you click anywhere on the 5-most-right columns. So if X is 11 or greater. You will get this error. Uncaught TypeError: Cannot read property '7' of undefined Where 7 is the Y axis of where you clicked.

Here is my SSCCE.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>    
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script type='text/javascript' src='graphstar.js'></script>
<script type="text/javascript">
    var board;
</script>
<script type='text/javascript' src='astar.js'></script>
<script type="text/javascript">
    $(document).ready(function()
{
        // UP to DOWN - 10 Tiles (Y)
        // LEFT to RIGHT - 15 Tiles (X)
        graph = new Graph([
        [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1], 
        [1, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 1], 
        [1, 13, 1, 13, 13, 13, 13, 13, 1, 1, 1, 1, 1, 13, 13, 1], 
        [1, 13, 1, 1, 13, 1, 1, 13, 1, 13, 13, 1, 13, 13, 13, 1], 
        [1, 13, 13, 1, 1, 1, 13, 13, 1, 13, 13, 1, 1, 1, 13, 1], 
        [1, 13, 13, 1, 13, 1, 13, 13, 13, 13, 13, 1, 13, 13, 13, 1], 
        [1, 13, 13, 13, 13, 1, 13, 13, 13, 13, 13, 1, 13, 13, 13, 1], 
        [1, 13, 1, 13, 13, 13, 13, 13, 1, 1, 1, 1, 13, 13, 13, 1], 
        [1, 13, 1, 1, 1, 1, 13, 13, 13, 13, 1, 13, 13, 13, 13, 1], 
        [1, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 1], 
        [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
        ]);
        //Let's do an example test.
        start = graph.nodes[1][2]; // x - y (15 columns across, 10 rows down)
        end = graph.nodes[12][7]; // x - y (15 columns across, 10 rows down)
        result = astar.search(graph.nodes, start, end);
    });
</script>
</head>
<body>
Loading... pathfinding. Look in Chrome Console/Firefox Firebug for more information.
</body>
</html>

As you can see, my game is jQuery. Also there is graphstar.js and astar.js. Don’t worry about astar.js because it works fine. graphstar.js is the where my problem is. astar.js is where the nodes and such are laid out. graphstar.js is where the map is graphed.

See the whole graphstar.js here: http://pastebin.com/kx4mw86z (Here is astar.js: http://pastebin.com/wtN2iF15)

This is where it’s laid out in graphstar.js:

// Creates a Graph class used in the astar search algorithm.
function Graph(grid) {
    var nodes = [];

    var row, rowLength, len = grid.length;

            for (x = 0; x <= 10; x++) {
             row = grid[x];
             nodes[x] = new Array(15);
                for (y = 0; y <= 15; y++) {
                   nodes[x][y] = new GraphNode(x, y, row[y]); 
                }
            }

    this.input = grid;
    this.nodes = nodes;
}

I know that my X‘s highest is 15 while my Y‘s highest is 10. But I tried messing around with it.. and I would get errors. Sometimes no errors and the page would get stuck.

Help?

New graphing format:

for (y = 0; y <= 10; y++) {

    row = grid[y];
    nodes[y] = new Array(15);

    for (x = 0; x <= 15; x++) {

        console.log("X: " + x + " Y: " + y);
        //console.log("Row: " + row[x]);
        nodes[x][y] = new GraphNode(x, y, row[x]);
    }
}
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1 Answer

  1. Editorial Team

    If I’m understanding this all correctly, I think you just have your indexes backwards.

    graph.nodes[12][7]

    graph.nodes[12] is undefined because there are only 11 elements in nodes:

    for (x = 0; x <= 10; x++) {

    nodes[x] = new Array(15);  // x only goes up to 10

    EDIT:

    This comment says it all:

    // UP to DOWN - 10 Tiles (Y)
// LEFT to RIGHT - 15 Tiles (X)

    This is backwards. You do not have 15 x and 10 y, you have 10 x and 15 y.

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