jQuery get the id/value of element after click function

$("#myid li").click(function() {
    alert(this.id); // id of clicked li by directly accessing DOMElement property
    alert($(this).attr('id')); // jQuery's .attr() method, same but more verbose
    alert($(this).html()); // gets innerHTML of clicked li
    alert($(this).text()); // gets text contents of clicked li
});

If you are talking about replacing the ID with something:

$("#myid li").click(function() {
    this.id = 'newId';

    // longer method using .attr()
    $(this).attr('id', 'newId');
});

Demo here. And to be fair, you should have first tried reading the documentation:

• http://api.jquery.com/category/selectors/
• http://api.jquery.com/category/events/
• http://api.jquery.com/attr/