Avoid same option selected multiple times using jquery

Answer 1

You are selecting all the options instead of in the current table.

Live Demo

Change

$('option[value=' + $(this).val() + ']:selected')

To

$(this).closest('table').find('option[value='+$(this).val()+']:selected')

You can make single handler instead of multiple for each row and further simplify and optimize code like this.

$('select').change(function () {
    if ($(this).closest('table').find('option[value=' + $(this).val() + ']:selected').length > 1)
    {
        alert('option is already selected');
        $(this).val($(this).find("option:first").val());
    }
});