<!DOCTYPE html>
<html>
<head>
<style>
div { background: white; }
.red { background: red; }
.red.green { background: green; }
</style>
<script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
<div>This div should be white</div>
<div class="red">This div will be green because it now has the "green" and "red" classes.
It would be red if the addClass function failed.</div>
<div>This div should be white</div>
<p>There are zero green divs</p>
<script>
$("div").addClass(function(index, currentClass) {
var addedClass;
if ( currentClass === "red" ) {
addedClass = "green";
$("p").text("There "); //改变文本
}
return addedClass;
});
</script>
</body>
</html>
