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accessing dynamically created iframe contents/elements like textbox, label from javascript

i am dynamically creating an iframe then calling aspx pages into it, what i need to do is access the elements of the iframe page and change its ( only specific element like text box or label etc.) value without reloading the whole page.
the first task is to access the elements of pages being called into my iframe, i am trying to acess them with javascript but no progress so far.
i have tried various solution like this :
How to get the body's content of an iframe in Javascript?

Actually, the answer you've attached should work. But note that this is only true in case that your parent page and the iframe URL are loaded from the same host (domain name). if not, you will get an error message from your browser stating that this operation is blocked.
If you are trying to show another site through and iframe and then manipulate it then you have to give up this dream because it can't happen that simply.
I can think of one solution for you, not sure about the legality of it, and it is kind of a pain in the ass.
You can open up a server side script on your own domain that receive a URL, fetches it's content and then echo it. This way you get the original desired page contents but you have it on your own host so you can manipulate it as mention in the attached answer.
Note that it's not easy at all to control from there, because once a user clicks a link in the page his out of your control again, so you may want to change all the page links to the address of your server side script and attach the original link to let it fetch it for you. Probably a lot more issues that i haven't thought about.
PHP Example of such a function:
function fetchURL() {
$urlToFetch = urldecode($_GET['url']);
$contents = file_get_contents($urlToFetch);
// maybe here manipulate links and other stuff throw str_replace or,
// if you want more control over it, you may want to load it in to some DOM parser class,
// manipulate it and extract the result back to a string variable.
echo $contents;
}
Note that in that case you should load the script through the iframe with the desired URL as a query string like that:
$yourDesiredURL = 'http://www.example.com';
echo '<iframe src="http://www.yourdomain.com/your/script/path.php?url=' . urlencode($yourDesiredURL) . '"></iframe>';
*************** EDIT *****************
Actually now i see that you tagged .NET, so my example code is probably not the best for you, but since it's very short and simple it wouldn't be any problem converting it.
Again, i want to say that iv'e never tried it and it's probably over your (and my) head, maybe you better give up on the idea.

Javascript onload after redirect

in my Javascript code I am loading a page, and then would like to perform some functions. I tried to use solutions like window.onload, but that is after my html (blank page with just the JS) loads, I need the function to perform after the page I am reffering to is loaded.
I am using this code:
this.document.location.href = myurl;
And after this loads, I would like to call some function. Is there a way to do so?
Thanks
EDIT:
I can not edit the target page source code.

When you change the value of document.location.href, you are essentially doing a redirect.
You can either just do whatever you want to do within the loaded page itself or if you don't have cross domain issues, do xhr of the page you're wanting to load dynamically, query the body, replace content of your current body and also replace head contents i.e. style, title and scripts etc. You could then execute any script you want.
Extra note: This is quite a tricky thing to do, I've done this a few times before - and its proven quite problematic due to the fact that you don't actually get a fully parsed document object that you can just query so simply, you only receive a huge string. One hack that I've thought of using is actually just loading everything within an iframe allowing easy querying which is actually documented - extra reading here

window.load takes forever to fire because it waits for all images and assets to load on the page.
It sounds like the best solution for you would be to poll for the document to be finished loading. Here's a simple example:
(function poll(){
if(document.readyState === "complete"
{
// Your code here
}
else
setTimeout(poll,500);
})();

Place the 'window.onload = myFunction(){...}' inside the page, which will be loaded.
this.document.location.href
will open the page like you typed it into the browser address bar and your onload-script in the old page will not be executed in the new one.
By the way, you can shortcut it to document.location = myUrl
See the Document-API at Mozilla

Load pages via AJAX and execute javascript and CSS

I've been searching for a while now, but I can't figure out how to load an entire page via AJAX and still execute all javascript and css.
Mostly I just end up with the plain text without any CSS.
Is there a way to do this? I tried jQuery.get, jQuery.load and jQuery.ajax, but none really work like that.

I have a different solution. You may try it with an iframe. Use jQuery to append an iframe script including all relevant codes into some part of your page (like some div). This may do it for you including CSS, like;
$('<iframe src="your_page.html"/>').appendTo('#your_div');
Or you may try something like;
$('<iframe src="your_page.html"/>').load(function(){
alert('the iframe is done loading');
}).appendTo('#your_div');

I have solved similar problem as following.
Download the webpage over ajax
Iterate it over and find any <script> and </script> tags
Get content from within these tags as text
Create new <script> element and insert there the code
Append the tag to your webpage
Another thing is you will need to somehow call the script..
I have done it this way:
I set standardized function names like initAddedScript callback which I am calling after appending the script to the page. Same as I have deinitScript called when I do not need the code (and its variables,..) anymore.
I must say this is awful solution, which likely means you have bad application architecture so as I have had:)
With css is it the same, but you do not need any handlers. Just append the style tag to your documents head.

If the page you load doesn't have any style data, then the external stylesheets must have relative paths that are not correct relative to the invoking document. Remember, this isn't an iFrame - you aren't framing an external document in your document, you're combining one document into another.
Another problem is that loading your complete page will also load the doctype, html, head, and body tags - which modern browsers will cope with most of the time, but the results are undefined because it's not valid HTML to jam one document into another wholesale. And this brings me to the third reason why it won't work: CSS links outside of the head section aren't valid, and the misplaced head section caused by your haphazard document-in-document collage.
What I'd do for compliance (and correct rendering) is this, which would be implemented in the Success callback:
Copy all link elements to a new jQuery element.
Copy the contents of all script in the head section
Copy the .html() contents from the loaded document's body tag
Append the link elements (copied out in step 1) to your host document's head
Create a new script tag with your copied script contents and stick it in the head too
Done!
Complicated? Kind of, I guess, but if you really want to load an entire page using AJAX it's your only option. It's also going to cause problems with the page's JavaScript no matter what you do, particularly code that's supposed to run during the initial load. There's nothing you can do about this. If it's a problem, you need to either rewrite the source page to be more load-friendly or you could figure out how to make an iFrame suit your needs.
It's also worth considering whether it'd work to just load your external CSS in the host document in the first place.

I suppose you are looking for something like this:
your page div --> load --> www.some-site.com
After a quik search the closest solution seems to be the one by "And": Load website into DIV
You have to run a web server and create a proxy.php page with this content:
Then your JQuery load() function should be like this:
$("#your_div_id").load("proxy.php?url=http://some-site.com");
NB. I have tested this solution and it should not load all the CSS from the target page, probably you'll have to recreate them. For example the image files stored on the remote server will not loaded, I suppose due to authentication policy.
You will be also able to view only the target page without the possibility to browse the target site.
Anyway I hope this could be a step forward to your solution.

Get your entire webpage as text using ajax
document.open();
document.write(this.responseText);
document.close();
OR
document.documentElement.outerHTML = this.responseText;
But you need to change the path of css and js pages in original webpage if the resulting webpage is in another directory.

Data scraping the page JUST written with PHP

I have a page that's written with PHP, and after the PHP writes it, I want be able to search through the HTML source code to find certain tags. Is this impossible/unwise?
I tried using file_get_contents at the end of the script when everything has technically already been written to the HTML, and I think I might have broken my page temporarily that way (Hit a resource limit on my host)
My main goal is trying to figure out how I can use Javascript to alter elements of my page one by one. Which I figure I could do if I could find the html tags I'm trying to change...which the PHP wrote...in the same page.
Very new to Javascript you see.

You could do this fairly easily, client side, with jquery.
If you absolutely need to process it server side with php and you absolutely can't do it while generating the code, you could use ob_start() to capture the output and then ob_get_contents() to drop it into a string before doing ob_end_clean() to flush it to the browser.

You can just right click on your rendered web page in most browsers and choose some variant of 'View Source'. Or, you can cURL your page's content, and view it as a text file.
Also, file_get_contents(); makes a new request to get a page / file's contents. So, if you load a page, and at the bottom, it tries to get the page content, it's going to load a new page, then another, forever. You're creating an infinite loop, and exhausting your allocated resources, as dictated by your hosting provider.

if I did not understand wrong, after page is loaded you want to change your own html output so,
<?php
echo "<div id='mydiv'></div>";
?>
<script type="text/javascript">
window.onload = function() {
document.getElementById("mydiv").innerHTML = "updated html";
}
</script>

Unless you're capturing the output as you generate the page, e.g.
<?php
ob_start();
.... page building here ...
$page = ob_get_clean();
echo $page;
?>
there will be NOTHING for you to work on. However, if you are capturing as above, then you can simply feed $page into DOM and manipulate it there.
But this begs the question... if you need to change the page after it's been built, why not just change how it's built in the first place?

jQuery append doesn't work fully with <script> tag

Appending a script element using jquery rather than putting it in the html by hand seems to lead to very different results. For instance
snaphtml = '<script src="http:\/\/seadragon.com\/embed\/lxe.js?width=auto&height=400px"><\/script>';
$('#content').append(snaphtml);
destroys the layout of my page, but putting the script element in the page directly works fine.
I have posted a test case online:
Working example with script in html.
Broken example with script appended via jquery.
The second div should not be deleted / invisible once the silverlight object is added.
Ideas?

I would recommend you to use $.getScript method for loading external script files programmatically:
$.getScript('path/to/script.js', function() {
alert('Script loaded.');
});
The script load is made asynchronously, and as you see in the above example, you can specify a callback function that will be executed when your external file has been loaded and is ready to use.

Tristan, you will not be able to include the script you reference dynamically onto the page after it has finished loading. The external script is using document.write which will only work correctly when called before the page has finished loading. This is why your static implementation works fine, and your dynamic one tears the page apart.
You might want to put together a dummy HTML file that just has a basic HTML structure and this script in it already. Then dynamically add an iframe to your page that loads the HTML. There are even more dynamic ways to make it work with an iframe, but that would be the easiest.

Try to use $.getScript:
$.getScript("http://seadragon.com/embed/lxe.js?width=auto&height=400px");
Edit:
The provided script is using document.write, which is likely causing your problems: you cannot add it dynamically at the middle of the page. Try loading SeaDragon as shown here:
http://www.seadragon.com/developer/ajax/getting-started/

try to break script tag like
snaphtml = '</sc'+'ript>'