How to verify the form on the parent page in iframe

Sometimes we need to verify the parent form in iframe, which is actually very simple. In iframe, we can use the parent keyword to call the javascript function of the parent page. The following is an actual problem I encountered in the project. For future convenience, record it. It would be better if it could be useful to everyone.

Iframe Form Design:

<Form name = "add" method = "POST" enctype = "multipart/form-data" action = "ecms. php "onsubmit =" return chkinput (this); "> <input type = hidden value = <? = $ Enews?> Name = enews> <input type = hidden value = <? = $ Classid?> Name = classid> <input name = id type = hidden id = "id" value = <? = $ Id?> <Input type = hidden value = "<? = $ Filepass?> "Name = filepass> <input name = mid type = hidden id =" mid "value = <? = $ Mid?> <? Php @ include ($ modfile);?> <Input type = "submit" name = "addnews" value = "publish" class = "login_button"> </form>

In iframe, write the code for verifying the parent page above and below:

<script type="text/javascript">function chkinput(form){//parent.CheckField();return parent.CheckField();}</script>

Form of the parent page:

<Form name = "classid" id = "classid" method = "post" action = "AddInfo. php "target =" myFrame "onsubmit =" return CheckChangeClass (); "> <select name =" ClassSelector_Type: dbl_Class "id =" ClassSelector_Type_dbl_Class "class =" input "onchange =" ResetClassItem () "> <option value =" 50_0 "> select a large topic </option> <option value =" 58_1 "> real estate information </option> <option value =" 61_1 "> education and Training </option> <option value = "64_1"> Talent Market </option> <option value = "67_1"> life information </option> <option value = "70_1 "> eat, drink, and play </option> <option value =" 73_1 "> dating and marriage </option> <option value =" 75_1 "> local mall </option> <option value =" 76_1 "> vehicle sales </option> <option value =" 85_1 "> household appliances/Digital Communication </option> <option value =" 86_1 "> decoration/home/Building Materials </option> <option value = "87_1"> Financial commerce </option> </select> <select name = "ClassSelector_Type: dbl_ClassItem "id =" ClassSelector_Type_dbl_ClassItem "class =" input "onchange =" ResetClassTypeTradeType (); document. classid. submit (); "> </select> <div style =" display: none; "> <input name =" ClassSelector_Type: txt_ClassId "type =" text "value =" 50 "id =" ClassSelector_Type_txt_ClassId "/> <input name =" ClassSelector_Type: txt_TypeId "type =" text "value =" 50_0 "id =" ClassSelector_Type_txt_TypeId "/> <input name =" ClassSelector_Type: txt_TradeType "type =" text "value =" 2 "id =" ClassSelector_Type_txt_TradeType "/> </div> (select a topic for easy information Review) </form>

Form Verification code on the parent page:

<Script language = "JavaScript"> function aa () {alert ("OK! "); Return false;} function CheckField () {var form_class_id = document. getElementById ("inline"); // alert (form_class_id.value); if (form_class_id.value = '50' | form_class_id.value = '') {alert (" select a topic "); return false;} return true;} </script>