此函数必须返回一个或多个空格分隔的class名,如果第二个参数是callback,那么需要返回的是属性值,函数传参解释如下:
1.index参数为对象在这个集合中的索引值
2.class参数为这个对象原先的class属性值
实例:
<!DOCTYPE html> <html lang='zh-cn'> <head> <title>Insert you title</title> <meta http-equiv='description' content='this is my page'> <meta http-equiv='keywords' content='keyword1,keyword2,keyword3'> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <!-- <script type='text/javascript' src='./js/jquery-3.0.0.js'></script> --> <script type='text/javascript' src='./js/jquery-1.12.1.min.js'></script> <style type='text/css'> input{font:400 13px/20px 'Courier New';color:#000;} .addOne{padding:0 8px;} .addTwo{color:#999;} </style> <script type='text/javascript'> $(function(){ $('#user').addClass('addOne addTwo'); }); </script> </head> <body> <input type='text' id='user' required="required" value='user'/> </body> </html>