I need to select an element like this: <div class="class_1 class_a"></div>
and I've found that both of the following work: $(".class_a").filter(".class_1").css("background-color", "red"); $(".class_a.class_1").css("background-color", "red"); The first one makes sense and is documented on the website. But the second one isn't documented anywhere as far as I can tell. My question is this: is this, i.e. $(".class_a.class_1") intended, documented behavior or is this some fluke that is likely to disappear? Is there a URL where this behavior is documented? I would like to use the second selector syntax (i.e., $(".class_a.class_1") ) but don't want to rely on it if it's likely to disappear. Thanks!