Question

I am have now this code: http://jsfiddle.net/DK67k/2/
In here is 2D tile map and when you click on tile you get coordinates on alert.
But for get precises coordinate you need click on top left tile(tiles is 16×16) and if I click on bottom right tile I am get second tile coordinates.

Maybe anyone have idea how to fix this?

Answer 1

Blaus’ answer is correct.
Though you might want to subtract the canvas offset left- and top position to make your canvas element available for dynamic positioning, and not relative to the 10px padding.

function mouseCheck(e) {
    var x = e.pageX - canvas.offsetLeft;
    var y = e.pageY - canvas.offsetTop;
    mouseX = Math.floor(x / 16);
    mouseY = Math.floor(y / 16);
}