How to Check a Checkbox is Checked or Not Using Java Script.

Here I will explain how to Check a Checkbox is Checked or Not Using Java Script.
just put this function on button click event where you need to validate.

 function SelecteAtleastOne() {

            var IsChecked = 0;
            var gridView = document.getElementById("<%=UltGrdResult.ClientID %>");//Grid Id
            var checkBoxes = gridView.getElementsByTagName("input");
            for (var i = 0; i < checkBoxes.length; i++) {
                if (checkBoxes[i].type == "checkbox" && checkBoxes[i].checked) {
                    return;
                }
            }
            alert('Please select at least One Record..!');
            return false;
        }