selected = $('#para-1');                    //仅选择JavaScript
selected = $('p.color-red.color-green');    //仅选择Erlang
selected = $('.color-red');                 //选择JavaScript和Erlang
selected = $('#test-jquery>p');                      //选择所有编程语言
selected = $('input[name="name"]');         //选择名字input
selected = $('input[name="name"], input[name="email"]');//选择邮件和名字input