Question

I’m trying to create a simple button manager to select and eventually unselect allready checked img elements which contains CSS class .my_class, why this doesn’t work?

var last_selected;
$("img.my_class").click ( function () {
    if (last_selected != null) alert ($(this) == last_selected); // returns false everytime
    last_selected =  $(this);
});

Answer 1

Each time you wrap this you create a new jQuery object. Two jQuery objects are not equal to each other just because they wrap the same element ($(this) != $(this)).

Instead, assign this itself to last_selected and everything should work as expected.

var last_selected;
$("img.my_class").click ( function () {
    if (last_selected != null) alert (this == last_selected);
    last_selected = this;
});