源代码
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>编程字典</title> </head> <body> <form action="demo_form.php"> <textarea rows="4" cols="50" name="comment" required> </textarea> <input type="submit"> </form> <p><b>注意:</b> IE9 和早期版本或者Safari 不支持required 属性</p> </body> </html>
运行结果