Truy vấn theo ID
RUN
<!DOCTYPE html> <html> <head> <title>Add Class jQuery</title> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <script language="javascript" src="https://code.jquery.com/jquery-2.0.0.min.js"></script> <script language="javascript"> function length_1() { var element = $('#container'); alert(element.length); } function length_0() { var element = $('#id_not_found'); alert(element.length); } </script> </head> <body> <div id="container"></div> <input type="button" value="Length = 1" onclick="length_1()"/> <input type="button" value="Length = 0" onclick="length_0()"/> </body> </html>
PHÓNG TO