Avoid same option selected multiple times using jquery

Answer 1

$('#table1 tr').each(function() {
    $(this).find('select').change(function() { //alert($(this).val())
        if ($('#table1 tr td select  option[value=' + $(this).val() + ']:selected').length > 1) {
            alert('option is already selected');
            $(this).val($(this).find("option:first").val());
        }
    });
});

$('#table2 tr').each(function() {
    $(this).find('select').change(function() { //alert($(this).val())
        if ($('#table2 tr td select option[value=' + $(this).val() + ']:selected').length > 1) {
            alert('option is already selected');
            $(this).val($(this).find("option:first").val());
        }
    });
});