How do I check if a textfield in iframe is empty? - javascript

Pretty much the question sums it up. I'm trying to do something similar to Gmail, where if you've entered stuff in a text field then the website will prompt you to to confirm if you want to leave the page.
But what if the text field in question is in an iframe? Obviously I can assign the iframe an id, but is there any javascript command or something that can check if a field in an iframe is empty or not? Is this even possible?
Edit: The iframe source and page the iframe is embedded in are from the same domain.

var value = document.getElementById('iframeID').contentDocument
.getElementById('theTextBoxId').value;
And yes, it's possible, you just need to get access to the <iframe> document with contentDocument.
From the DOM iframe element, scripts can get access to the window object of the included HTML page via the contentWindow property. The contentDocument property refers to the document element inside the iframe (this is equivalent to contentWindow.document), but is not supported by Internet Explorer versions before IE8.
Scripts trying to access a frame's content are subject to the same-origin policy, and cannot access most of the properties in the other window object if it was loaded from a different domain.
MDN

Just set onbeforeunload as you would as if the iframe'd page were the top-level page. If you try to navigate away in the parent frame or the child frame, it will be interrupted by the confirmation.

Using JQuery you can access the iframe content:
$("#iFrame").contents().find("#text")

Related

load event inside iframe

I am trying to run some javascript inside an iframe after it loads and am having trouble. I'm not sure if it means my concept of what is happening is wrong or if my code is just wrong.
What I want to do is load a javascript file in the iframe environment and then call a function. (the iframe contents are static web pages captured with singlefile and served from my server. I want to be able to pop up menus for the images in the iframe page). Is this possible, or is it blocked for security considerations? I can get the contentDocument from the iframe and see what is in it but not make any changes to it. Adding a load event listener to the iframe runs in the top-level DOM, not the iframe.
An ugly workaround would be to add a line loading the script to each of my served html files, but I'm reluctant to do that since it seems kind of fragile. Is that my only option?
you can select the iframe element and access its internal window object.
to do this first assign an id to your iframe element
<iframe id="chosen-iframe" ...></iframe>
and to access the window use the following
const iframe = document.getElementById('chosen-iframe');
const iFrameWindowElement = iframe.contentWindow;
and with access to the window, you can create a script tag that contains the script you want to inject inside the iframe
var injectedScript = iFrameWindowElement.document.createElement("script");
injectedScript.append(...);
iFrameWindowElement.document.documentElement.appendChild(script);

Is there a way to prevent an iframe from redirecting parent window, but in such a way that "top level" redirects still work inside the iframe itself?

So I've read about the HTML5 sandbox property and I understand that if I want to prevent an iframe redirect its parent window I can use the sandbox property leaving allow-top-navigation out. However when this is done, if the iframe was originally relying on top level redirection, what happens in its place is that it redirects to a blank page, effectively breaking navigation.
Can I prevent the iframe from tinkering its parent window while still allowing "top level" redirects, only letting these work within the context of the iframe instead of being top level?
Edit: For context, I'm working with a third party and its page has a form with a target _top. If the iframe is sandboxed, upon submitting the form users get a blank page, if it's not sandboxed the entire page is redirected. I'm looking for something that would allow to submit the form and show the result within the iframe itself.
With HTML5 the iframe sandbox attribute was added.
At the time of writing this works on Chrome, Safari, Firefox and recent versions of IE and Opera but does pretty much what you want:
Allows the iframe content to be treated as being from the same origin as the containing document
<iframe src="url" sandbox="allow-same-origin"></iframe>
Browser Compatibility
Some Useful links
w3schools for sandbox
developer.mozilla.org iframe
-
You can use the onbeforeunload property and determine if you wan to redirect or not.
Here is the docs page for it
Basically what I would try is this:
Make a function that adds the sandbox attribute with everything, just leaving out the allow-top-navigation, to the iframe
Bind a function to the onbeforeunload property of the iframe that calls the function that adds the sandbox attribute (be sure not to return anything because a dialog will pop-up)
This should work because the request is made in the iframe first, and then we can prevent it from carrying over to our top level window.
Another thing you should check is if you maybe left out the allow-formsoption, which can cause what you are describing.
Please let me know if any of this worked.

Complete isolation of javascript in the iframe from the same domain

Assume we have a window and an iframe with some javascript in it. The iframe sourcecode is defined directly in "srcdoc" attribute of the iframe.
Is it possible to somehow force the browser to behave like the iframe is loaded from another domain?
I mean I don't want the javascript in the iframe to be able to access the main window via "window.parent" or anything like that, because the iframe contents is not trusted. But the problem is that it's stored on the same domain and I even want to use the same request to load both the main window and the iframe contents (with that "srcdoc" attribute).
So is it possible at all?
Thanks!
You could prepend the string:
"<script> parent = top = null; </script>"
To the srcdoc. That should prevent the rest of the code in the srcdoc form accessing the parent through window.parent and window.top.
I'm not sure if there are any other ways to access the parent of an iframe.

Changing the contents of an iframe

I have an iframe embedded on my webpage and I'd like to edit certain parts of it using javascript. Is this possible and how would I do it?
Since the iframe is loading content from another domain — no. You'll hit the same origin policy.
According to the HTML DOM spec (level 2), you can reach the child DOM by using the .contentDocument property of the iframe's DOM node.
But, of course, no browser lets you do that across domains anymore...
You can get the iframe document by doing this:
document.getElementById(iframeId).contentDocument
That is if you own the page loaded in the iframe.

How do I build an iframe with the same domain as the page in Safari/WebKit

The scene: I'm writing an embeddable widget. It takes the form of a <script> tag, which builds an iframe containing everything it needs to display. The iframe has no src, and the script writes to it with theIframe.contentWindow.document.write(). This keeps the widget contained, and keeps element ids and script from conflicting with the page on which the widget is embedded.
The trick: The widget has to be able to change its size. To do this, it sets its containing iframe's style.height. This requires access to the outer page's DOM. In Firefox and IE, this is allowed, because the iframe's document and the outer document are considered to share an origin.
The twist: In Safari, however, the two documents are considered not to share an origin. The inner document is considered to be at about:blank, while the outer document is clearly using a different protocol and "domain" (if blank can be considered the domain).
The question: How can I build an iframe programmatically whose document Safari/WebKit will consider to have the same origin as the document of the window creating it?
Edit: After further experimentation, I can't find a way to programmatically create an iframe whose location is not about:blank regardless of whether I change its contents.
If I create the frame with document.createElement(), give it a src which points to a real HTML resource on the same origin called "foo.html", and document.body.appendChild() it, Safari's console shows the element as expected in the DOM, but the contents of the page do not appear, and the document is listed in the sidebar as "about:blank".
If I include the HTML for the iframe directly in the page, the contents of foo.html appear, and "foo.html" appears in the sidebar.
If I insert the HTML using document.write(), I get the same result as with document.body.appendChild().
Both programmatic versions work in Firefox.
The best suggestion I could give is to have the iframe set to a blank page on the same server (ie blank.html) and then edit the content. A pain in the rear, I know but it's a workaround.
You could also try
iframe.contentDocument.open("replace");
iframe.contentDocument.write("<b>This is some content</b>");
iframe.contentDocument.close();
However, I'm not sure if that only works in IE. Sorry I couldn't be more helpful than that.
Aha. This seems to be a bug in WebKit. When an iframe is created programmatically, its src attribute is ignored. Instead, the frame defaults to about:blank and must be directed to a URL to point elsewhere. For example:
theIframe.contentWindow.location = theIframe.src

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