Need to optimise jQuery functions

Question

1 set:

$('#tabs li:first-child').addClass('first-child');
$('.photos li:first-child').addClass('first-child');
$('#alphabet li:first-child').addClass('first-child');

2 set:

$(function(){
    $("#header-thumbs img").fadeTo("fast",1);
    $("#header-thumbs img").hover(function(){
     $(this).fadeTo("fast",.7)},function(){
     $(this).fadeTo("fast",1)})});
$(function(){$(".catalog dt img").fadeTo("fast",1);
    $(".catalog dt img").hover(function(){
     $(this).fadeTo("fast",.7)},function(){
     $(this).fadeTo("fast",1)})});
$(function(){$(".photos li img").fadeTo("fast",1);
    $(".photos li img").hover(function(){
    $(this).fadeTo("fast",.7)},function(){
    $(this).fadeTo("fast",1)})});

Is it possible to optimize, for a less code?

---

Thanks Paolo Bergantino for his help, the result is:

Optimized and packed first set (540->171):

$(function(){$("#header-thumbs, .catalog dt, .photos li").find("img").fadeTo("fast",1).hover(function(){$(this).fadeTo("fast",.7)},function(){$(this).fadeTo("fast",1)})});

second set (158->78):

$('#tabs, .photos, #alphabet').find('li:first-child').addClass('first-child');

Used Dean Edwards packer

Answer 1

It is common practice when dealing with sets of elements and CSS/Javascript to give them all a similar class if at all possible to make them easier to work with. You could then just do this:

$('.mysimilarclass li:first-child').addClass('first-child');

If that's not an option, you could also just aggregate all the selectors into one:

$('#tabs, .photos, #alphabet').find('li:first-child').addClass('first-child');

For the second set the same thing applies. You can "group" them all with one class, or just aggregate all the selectors you want and then only find images from them. Plus, you can take advantange of jQuery's chaining to not query the DOM more than once:

$(function(){
    $("#header-thumbs, .catalog dt, .photos li")
     .find("img")
     .fadeTo("fast", 1)
     .hover(function() {
         $(this).fadeTo("fast", .7);
     }, function() {
         $(this).fadeTo("fast", 1);
     });
});

Also, if at all possible, it is good practice to always add what element is expected to have a class in your selectors. So instead of .photos li it is better to do ul.photos li or whatever element will have a class of photos. This is not always possible, of course, but it is advisable whenever it is.