We Keep Coding

Google Tag Manager and Single Page APP: How to read a DOM Element?

I want to create a variable on my GTM to store a DOM element. I've tried a custom javascript, for example:
function(){
return document.querySelector('.room__price-value').innerText;
}
But nothing, on GTM preview I see always NULL. I think the issue was the single page app.
And I can't involve the programmers.
Any suggestions?
Thanks

Make sure that when in preview, you check the value of your variable on every event on the left.
Make sure when you execute document.querySelector('.room__price-value').innerText; in your console, you actually get the result you're expecting.
Change the code until you get the result in the local console.
Make sure your timing is good, as Eike mentioned in the comment.
What you're doing there seems right. That's pretty much how you do DOM scrape in GTM when front-end devs aren't available. If the suggestions still don't work for you, give us more info on what you're doing, on how your DOM looks like, what your debugging showed and such. As much potentially useful context as you can.

jQuery on MTurk, why does Chrome report "Unsafe JavaScript attempt to access frame with URL"?

I'm doing a couple of things with jQuery in an MTurk HIT, and I'm guessing one of these is the culprit. I have no need to access the surrounding document from the iframe, so if I am, I'd like to know where that's happening and how to stop it!
Otherwise, MTurk may be doing something incorrect (they use the 5-character token & to separate URL arguments in the iframe URL, for example, so they DEFINITELY do incorrect things).
Here are the snippets that might be causing the problem. All of this is from within an iframe that's embedded in the MTurk HIT** (and related) page(s):
I'm embedding my JS in a $(window).load(). As I understand it, I need to use this instead of $(document).ready() because the latter won't wait for my iframe to load. Please correct me if I'm wrong.
I'm also running a RegExp.exec on window.location.href to extract the workerId.
I apologize in advance if this is a duplicate. Indeed - after writing this, SO seems to have a made a good guess at this: Debugging "unsafe javascript attempt to access frame with URL ... ". I'll answer this question if I figure it out before you do.
It'd be great to get a good high-level reference on where to learn about this kind of thing. It doesn't fit naturally into any topic that I know - maybe learn about cross-site scripting so I can avoid it?
** If you don't know, an MTurk HIT is the unit of work for folks doing tasks on MTurk. You can see what they look like pretty quick if you navigate to http://mturk.com and view a HIT.
I've traced the code to the following chunk run within jquery from the inject.js file:
try {
isHiddenIFrame = !isTopWindow && window.frameElement && window.frameElement.style.display === "none";
} catch(e) {}

I had a similar issue running jQuery in MechanicalTurk through Chrome.
The solution for me was to download the jQuery JS files I wanted, then upload them to the secure amazon S3 service.
Then, in my HIT, I called the .js files at their new home at https://s3.amazonaws.com.
Tips on how to make code 'secure' by chrome's standards are here:
http://developer.chrome.com/extensions/contentSecurityPolicy.html

This isn't a direct answer to your question, but our lab has been successful at circumventing (read hack) this problem by asking workers click on a button inside the iframe that opens a separate pop-up window. Within the pop-up window, you're free to use jQuery and any other standard JS resources you want without triggering any of AMT's security alarms. This method has the added benefit of allowing workers to view your task in a full-sized browser window instead of AMT's tiny embedded iframes.

Using jQuery, I'd like to know when an event occurs in the body of Gmail's new email composition iframe

The specific area I'm trying to access is the body of the New Email Composition in Gmail.
More generally, this is the < BODY > of an iframe, within another iframe.
This is being used for a simple Chrome Extension that I'm trying to develop, so this might be asked, my manifest file has the proper setting for frames:
"all_frames":true
Thank you!

Hmmm. No one has ventured an answer.
I am sure this will be roundly shouted down and I am eager to see the right way to do it.
$('.Ak').live('click',function(){
$(this) //reference to the element
});
The class name is Ak for the compose textarea.
This is a pretty horrible kludge but it works and you can fix it latter if that is holding up progress on something else.
Also, you should take a look at the chrome extension "After The Deadline". The code is not super complex and he successfully hooks his spell checker into the GMail textarea.
I just found a blog from the creator of ATD where he describes his trials and tribulations dealing with frames and Chrome Extensions. That may actually be very helpful too even if you are not doing an extension.
http://blog.afterthedeadline.com/2010/05/14/how-to-jump-through-hoops-and-make-a-chrome-extension/

alternative when an older browser does not accept jquery

I have just been altered to the fact that a user of my website is using a very old browser which does not run jquery (in this case Safari 1.x) and as a result can not access the login panel which uses jquery's slideToggle function.
Can anyone think of a fix which detects whether a browser is able to use jquery - and if not make that link go to a different page rather than showing the login panel?

You could a little conditional check like
if(!'jQuery' in window) {
// jQuery is not available
}
or, if Safari 1.x doesn't know about the IN operator (I'm not sure) use
if(!window.jQuery) {
}

I think there are alternative answers to this, but for me, I would have to weigh up the time it will take you to support his obsolete browser (I'm sure there may be other things inside the site), versus the payback to you...

In the plain HTML source code for the the href= of the login link, set that to a plain HTML login page.
Using jQuery, attach the click handler to the link, if this part fails, thats ok, the browser will just follow the href in the link to the plain login page, allowing your old-browser-user to login still.
$(document).ready(function(){
$('#login_link_id').click(function(){
// Your code here
});
});

If you use javascript/jQuery you should ALWAYS ensure your site works perfectly without it. In this case if you have a login popup box; you probably assign a click event assigned after the DOM has loaded.
What you should do is ensure that if jQuery isn't present the link loads a "normal" login webpage as opposed to the popupbox. I use something similar to this:
Log in
<script>
if(!'jQuery' in window) {
$(document).ready(function(){
//assign on click event to loginlink
});
}
</script>
If jQuery doesn't exist then login.html will be opened normally.

Wow, seriously?! Safari 1.x?? Anyhow, try this...
var isJQSupported = false;
$(function() { //shorthand for document.ready
isJQSupported = true;
//your usual code
});
if (!isJQSupported) {
window.location = "http://www.apple.com/safari/download/";
}

To me it sounds like safari 1.X has problems with jQuery internally. Which means simple checks like whether $ exists in the global space or whether $(function) does anything are not going to help.
The most likely root cause will be that javascript throws an error in loading of jQuery itself which will then stop the rest of your javascript code from execution.
There are four viable options here.
Either make the website work with noscript. Replace your login control with pure HTML and postbacks and ask the user to turn javascript off. This option is useful since you won't be fixing the issue for safari 1.x problems specifically.
You can make javascript check for safari 1.X and other non-supported browsers and only load jQuery through script tag injection or ajax if your user is using a supported browser. If the user is using a browser not compatible with jQuery then you can instead use plain javascript.
Get a copy of safari 1.x and see why jQuery breaks. Then fix it and ask for it to pulled into the release of jQuery 1.5. This relies on the fix being something that does can be done without hacking and that the jQuery team agrees is worth adding in.
Ask the user to use a compliant browser.
There might be some more options. I would personally lean towards asking the user to use a compliant browser because supporting Safari 1.x is ridiculous.

This seems like a case where progressive enhancement is needed.
You have to do multiple checks
see if $ exists
see if $.fn exists
[not sure if needed] check if $.support is a function
check for feature support as needed with $.support() http://api.jquery.com/jQuery.support/
At the end of the check, when jQuery reports that features you need are present - the rest of the script can run.
If you're not sure which features mentioned in the support you use, then this might need a single test on Safari 1.x to see what are the values returned by $.support(), but that is what your nasty old-browser-user can do for you (if you prepare code and publish) and report the resulting text. Then you compare the list with other [old] browsers that are accessible and determine features that are required.
The easy way would be to require everything and cancel all scripts if suport for any feature is missing. This will also rule out IE6 and IE7 and opera below 9.something and firefox below 2.0 or including - I'm not sure.

Use a server side language to detect if it's the old safari based on user-agent and load a different javascript file

initialization of dojo widget

I tried to create custom widget for my site. when I loaded page it says:
mixin #0 is not a callable constructor.
clsInfo.cls.prototype is undefined
I can't find any information about clsInfo, so I don't know what is it. maybe the problem that I use dojo from google:
and my own script is located on localhost. so when my dojo on page initializes something goes wrong with my script. I can't find any good info on dojo, maybe I search in wrong places?
please help me to resolve my problem

I ran into this when I was trying to override a dijit.Dialog so I could bind events to controls within it. We've yet to see if the binding part will work, but if you look at the source, this happens when one of the bases passed in as the second argument fails to resolve to an "[Object function]". In my case, I was passing a String in.
dojo.declare takes 3 arguments:
The name of the custom object "class" you're building
An array of base classes, parents to provide functionality (not the string names of those classes)
A hash of functions and declarations
So if I want to override dijit.Dialog, I have to do:
dojo.declare("myDialogType", [dijit.Dialog], {
function1() {/*Code*/},
function2() {/*Code*/}
}
I had ["dijit.Dialog"] as my second argument and that was the problem.
I strongly recommend using Web Inspector or Firebug with uncompressed local copies of the Dojo library rather than the CDN to figure out what's going on and debug these types of problems. Dojo's documentation is extensive but not complete in some areas and some behaviors have to be figured out by looking at what the code expects. That's not intended as a slight to the authors; once you get it going it's a pretty awesome product, and any documentation for volunteer work is appreciated.

Are you sure Dojo is loading? Did you put your code in a dojo.addOnLoad()? When using a CDN you sometimes run into issues with execution times. dojo.addOnLoad() will not only trigger when the DOM is loaded, it gets called when dojo resources have downloaded, such as dijit._Widget.

I've run into this problem when I screw up the order of my requires which makes _WidgetBase not what _WidgetBase really is. Seems like a simple spot to screw up.