//addClass()
$("button").click(function(){
$("#div1").addClass("important blue");
});
//removeClass()
$("button").click(function(){
$("h1, h2, p").removeClass("blue");
});
//toggleClass()
$("button").click(function(){
$("h1, h2, p").toggleClass("blue");
});
//css()
$("p").css("background-color", "yellow");
$("div").addClass("important");
addClass() - Adds one or more classes to the selected elements
removeClass() - Removes one or more classes from the selected elements
toggleClass() - Toggles between adding/removing classes from the selected elements
css() - Sets or returns the style attribute