在重定向到另一个页面之前，在JavaScript的背后调用JavaScript函数

Question

I have Javascript function which i need to call at code behind in vb.net . The Main problem is it is not called properly because there is redirection to next page before this function executes. I do not want to call this function on Onclick event of button or something like that i want to call it after some specific condition in code behind. I have already tried following solutions please let me know if you have some other suggestions.

System.Web.UI.ScriptManager.RegisterClientScriptBlock(Page, Me.GetType(), "Script", "ShowEntryPermForm();", True)

Page.ClientScript.RegisterStartupScript(Me.GetType(), "Window", "ShowEntryPermForm();", True)

Problem Description: added from comment

The scenario is that in javascript function i have checked various conditions related to the project and it open up a pop up window where user enter his or her comments.

It is not necessary every time the function will open the pop up window. But by default the page redirects to new page as both the functions Javascript and redirection to another window are run on click event of the button.

But now my requirement is changed now i have to call the function from code behind in particular condition. Hope you get it now

Answer 1

You can do this in following way.

window.onbeforeunload = function()
{
    //your code goes here
    return "";
}

If you return anything here then browser will display and ask user whether to leave the page. In your case you don't need to return anything but runs the code.

Answer 2

The only way is to Separate the code and javascript in the way they will not rely on each other

for example you make an hidden asp:button with the rest of server side code

server side :

if(...) then
page.ClientScript.RegisterStartupScript(Me.GetType(), "Window", "ShowEntryPermForm();", True)
else
  page.ClientScript.RegisterStartupScript(Me.GetType(), "Window", "otherfunction();", True)
    end if

sub IDServersideHiddenbutton(obj as object ,e as eventargs)handles IDServersideHiddenbutton.click
rest of the server side code including the redirect
end sub

client side :

   javascript ShowEntryPermForm()
        {
      //  javascript code

    $("#IDServersideHiddenbutton").click();
    }

javascript otherfunction()
{
//just the click 

$("#IDServersideHiddenbutton").click();
}

I really don't know your code structure but You can manipulate it to work with this idea