Have shared an approach which will add the benefit of firing when a label associated with a checkbox is clicked.
$(document).ready(function() {
//set initial state.
$('#textbox1').val(this.checked);
$('#checkbox1').change(function() {
if(this.checked) {
var returnVal = confirm("Are you sure?");
$(this).prop("checked", returnVal);
}
$('#textbox1').val(this.checked);
});
});