Getting value from table cell in JavaScript

function GetCellValues() {
    var table = document.getElementById('mytable');
    for (var r = 0, n = table.rows.length; r < n; r++) {
        for (var c = 0, m = table.rows[r].cells.length; c < m; c++) {
            alert(table.rows[r].cells[c].innerHTML);
        }
    }
}