Register JavaScript?

See this sentence in the projectCode:

This . Prerender + =   New Eventhandler (pagejs_prerender );

 PrerenderThis is an event.PrerenderAdd a processing method for the event.

RegisterJSExample:

Registerclientscriptblock

///   <Summary>
/// Before the page is displayed, register JavaScript from the server to the front-end html
/// Display the lettertemplateparamerter of the current lettertemplate in the foreground
///   </Summary>
///   <Param name = "sender"> </param>
///   <Param name = "E"> </param>
Protected   Void Pagejs_prerender ( Object Sender, system. eventargs E)
{
System. Text. stringbuilder sb =   New System. Text. stringbuilder ();
SB. append ( " <Script language = \ " Javascript \ " > \ R \ n " );
If (Session [globalpara. seesion_show_alert_message] ! =   Null )
{
SB. append ( " Alert (' "   + Stringutil. jsscriptreplaceillegalstring (string) session [globalpara. seesion_show_alert_message]) +   " '); \ R \ n " );
Session. Remove (globalpara. seesion_show_alert_message );
}
SB. append ( " </SCRIPT> \ r \ n " );
String JS = SB. tostring ();
If ( ! Isclientscriptblockregistered ( " Pagejs_prerender " )) // Register JS
{
Registerclientscriptblock ( " Pagejs_prerender " , JS );
}
}

 Why registerJavascript? RegisterJavascriptWhat does that mean?

AboutRegisterclientscriptblockThe roles are not the same. Some say they are registered from the front-end to the back-end.JavascriptScript, some are registered from the background to the foregroundJavascriptScript.

My understanding of registering Javascript is vague.

 

Supplement:

Public   Static   Void Showerrormsg (page, String Errmsg)
{
String Scrpt =   " <Script language = 'javascript '> "
+   " Alert (' "   + Errmsg +   " '); </SCRIPT> " ;< P>

page. clientscript. registerstartupscript (page. getType (), " clientscript " , scrpt );
}

registerclientscriptblock generally returns the packaging of client functions, registerstartupscript returns the function that will be executed after the document is loaded. It is similar to the function in body onload = "F ()". The two methods have different positions in the Code presented by the client. registerclientscriptblock is after

, while registerstartupscript is before .