Check All Checkbox of a grid by using JavaScript

function CheckAllBox() {
    var chkval = document.getElementById('ctl00_cphMain_grdCategory_ctl01_chkAll').checked;
    try {
        for (var i = 2; i & lt; 200; i++) {
            if (i & lt; = 9) {
                document.getElementById('ctl00_cphMain_grdCategory_ctl0' + i + '_chk').checked = chkval;
            } else {
                document.getElementById('ctl00_cphMain_grdCategory_ctl' + i + '_chk').checked = chkval;
            }
        }
    } catch (e) {}
}