<form action="" method="post" onsubmit="check_form()"> 执行check_form函数 return false 无效继续提交表单
<form action="" method="post" onsubmit="return check_form()"> (√)
<form action="" method="post" onsubmit="check_form()"> 执行check_form函数 return false 无效继续提交表单
<form action="" method="post" onsubmit="return check_form()"> (√)