javascript function with __

[dbeez]

I'm looking at someone's javascript here in my console. The javascript has a

onclick="javascript:__doPostBack('Pager','2')"

function in it.

The only problem is though, that there is no __doPostBack function on the html or the .js file.

What does the __ mean to javascript ??
Why does the function seem to not be there ? and why does it work without it ?

 

[tsuji]

>What does the __ mean to javascript ??
None. Not in javascript as such. It may be a convention for the scripting team.

 

[BillyRayPreachersSon]

A quick search on Google shows that the "__doPostBack" function is probably associated with .Net controls.

Hope this helps,
Dan


[tt]Dan's Page [blue]@[/blue] Code Couch

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[/tt]

 

[dbeez]

if it's in the .net arch, then why is it denoted as

javascript:__doPostBack

I don't see this piece of the script being sent server-side, it appears to be a client-side script with no corresponding function. Maybe I'm missing something ??

 

[BabyJeffy]

Probably best to ask this in one of the .net forums. They'd know the answer.

Cheers,
Jeff

[tt]Jeff's Page [/tt][tt]@[/tt][tt] Code Couch

http://www.codecouch.com/jeff/

[/tt]

What is Javascript? faq216-6094

 

[dbeez]

That's probably a good idea Baby*

I know abosolutely nothing about .net, but the code does tend to suggest that this is javascript

<span class="page" onmouseover="this.style.background='#f7f7f7'" onmouseout="this.style.background=''" onclick="javascript:__doPostBack('Pager','8')">
8
</span>

... unless I'm mistaken ...

 

[BabyJeffy]

It is javascript... and it's, of course, not well formed. You do not need the string 'javascript:' in the onclick. But you are correct... a javascript function called __doPostBack() is being called when you click the span - and it is passing 2 strings back to the function.

The function itself will be in an include file. View source of the file using your browser... and look in the head of the file for a <script...></script> that brings in an external javascript file. I would expect it to be there somewhere.

You can alert the function using something like this in the location bar of your browser:

javascript:alert(window['__doPostBack']);

Cheers,
Jeff

[tt]Jeff's Page [/tt][tt]@[/tt][tt] Code Couch

http://www.codecouch.com/jeff/

[/tt]

What is Javascript? faq216-6094

 

[adam0101]

ASP.NET throws that function in there to submit the form on certain events and to alert the server of which element caused the event so the proper server-side event handling code can be executed.

If you view the source of the page after it's parsed, you'll see a block of code like this:

<input type="hidden" name="__EVENTTARGET" value="" />
<input type="hidden" name="__EVENTARGUMENT" value="" />
<input type="hidden" name="__VIEWSTATE" value="" />
<script language="javascript" type="text/javascript">
<!--
	function __doPostBack(eventTarget, eventArgument) {
		var theform;
		if (window.navigator.appName.toLowerCase().indexOf("microsoft") > -1) {
			theform = document.Form1;
		}
		else {
			theform = document.forms["Form1"];
		}
		theform.__EVENTTARGET.value = eventTarget.split("$").join(":");
		theform.__EVENTARGUMENT.value = eventArgument;
		theform.submit();
	}
// -->
</script>

Adam

http://adameslinger.blogspot.com/

 

[jemminger]

this is a function provided by ASP.NET. the two leading underscores mean nothing syntactically to javascript. this function MUST be included in your page in some manner otherwise it will not work, and the browser will throw an error when the function is called. if you do not see it explicitly defined on the page itself, then it is likely imported in some other javascript include file, or perhaps you are using frames and another frame has imported/defined it.

following BabyJeffy's lead, i went to a website with a .aspx form, typed "javascript:document.write(__doPostBack)" in the address bar, and received

function __doPostBack(eventTarget, eventArgument) {
	var theform;
	
	if (window.navigator.appName.toLowerCase().indexOf("microsoft") > -1) {
		theform = document.Form1;
	} else {
		theform = document.forms.Form1;
	}
	
	theform.__EVENTTARGET.value = eventTarget.split("$").join(":");
	theform.__EVENTARGUMENT.value = eventArgument;
	theform.submit();
}

also, searching MSDN for "__doPostBack" yields many results, one of which is:

http://msdn.microsoft.com/library/d...eneratingclient-sidejavascriptforpostback.asp

-jeff

http://www.jeffemminger.com

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