W3School TIY
编辑您的代码：
<!DOCTYPE html> <html> <head> <style> .full { border: 1px solid red; } </style> <script type="text/javascript" src="../jquery/jquery.js"></script> </head> <body> <ul><li>Does the UL contain an LI?</li></ul> <script> $("ul").append("<li>" + ($("ul").has("li").length ? "Yes" : "No") + "</li>"); $("ul").has("li").addClass("full"); </script> </body> </html>
查看结果: