canvas on click handler

canvasmouseinterface.js

function canvasOnClickHandler(event) {
        var hex = getCursorPosition(event);
        //action
       map.tilelist[hex.row][hex.column].whateverfunctionisinTILE();
      };

function getCursorPosition(event) {
        var x;
        var y;
        if (event.pageX || event.pageY) {
          x = event.pageX;
          y = event.pageY;
        } else {
          x = event.clientX
            + document.body.scrollLeft
            + document.documentElement.scrollLeft;
          y = event.clientY
            + document.body.scrollTop
            + document.documentElement.scrollTop;
        }

        x -= gridCanvas.offsetLeft;
        y -= gridCanvas.offsetTop;
        //map.MAPSIZE is the diagonal size of map, it should be computed in map, instead of here
        mapsize = Math.sqrt((map.getWidth()^2)+(map.getHeight()^2));
        var tile = new TILE(Math.floor((y - 4) / mapsize), Math.floor((x - 2) / mapsize));
        return tile;
      };
      
      gridCanvas.addEventListener("click", canvasOnClickHandler, false);
    } else {
      alert("Canvas is unsupported in your browser.");
    }