We use the dojo framework on our websites. A client has called in a panic saying their sales from users of Microsoft Edge have completely dropped off. I've found that in that browser, intermittently, the dojo variable is null after page load. So of course no interaction works for those users, so of course no sales.
But in the course of testing I found this astonishing thing in devtools:
I don't even know how I would do that if I wanted to do it. So I want to track this down but I have no clue what to look for. I might've suspected some weird, recurring setInterval code, but I would not have thought that could get between the two statements on that last console line.
There's a script line just before the </body> tag where I'm able to put a breakpoint. At that point, dojo is set as the framework as expected. So some code that loads after page load is doing it.
(EDIT: I'd be willing to do iterative, brute force breakpoints if I could. But I only have access to Edge via BrowserStack, and trying to set useful breakpoints in minified code is very difficult in Edge's dev tools.)
Does anyone have a suggestion what sort of thing I should look for?
How to debug for this? Is there a client-exposed variable where you can see the functions set to the document's onload, or a way I can put breakpoints in them?
I attempted using a watch() shim in console to watch for the dojo object being changed, but didn't have much luck with that. (but might have done it incorrectly, so if this is an idea, I might need help with proper implementation).
EDIT: There's also this, if this helps make any sense of it. After I delete dojo, setting it works as expected.
Well, I don't know what the specific problem is, but someone has at least given me a way in which this is possible:
window.__defineGetter__('dojo', function(){ return null })
This doesn't exist in the original code, but at least now I see how it's possible at all. The person who gave me this suggests that the code might be trying to get and protect its own copy of dojo, but something about it goes wrong in Edge.
Related
Is there any possibility to set the Internet Explorer settings by running Javascript file..?
I want to set the following settings in IE through javascript/Jquery
Go to, ‘Tools’ -> ’Internet options’.
Under ‘General’ tab, click the ‘Settings’ button in the ‘Browsing History’ section.
Choose the radio button "Every time I visit the webpage".
Click ‘OK’ and restart the IE.
This is not possible - it'd be a bit of a security hole if sites were able to do this...
Firstly, the short answer is no: You can't do what you're asking for.
Javascript within the browser is heavily restricted to only being able to access resources for the actual page being viewed. This is an important security feature.
You cannot access other pages or other tabs. You cannot access parts of the browser UI outside of the page itself. You cannot run external programs.
Even if you could, the way you've described it wouldn't work anyway: The settings page you've described is specific to one particular version of IE. So your hypothetical program wouldn't work in any other browser or even any other version of IE.
However, more importantly, you need to ask yourself why you're asking for this.
The thing is that you're trying to solve a problem with your site. You've found something that resolves it, and you've asked a question about how to automate that. But you need to work backward a bit -- stop trying to work out how to automate this particular solution: you need to ask yourself whether there might be a different way of solving the original problem, which could be automated.
The fact is this: the config setting you're trying to change is for handling how the browser deals with caching of files. There are ways of changing the behaviour of caching that can be scripted by your site. You might want to look at questions like this one for example.
The lesson here is this: Don't simply ask how to do something; explain why you're trying to do it as well. There might be an alternative solution that's better than the one you've thought of.
No, it's not possible to do using JavaScript.
This is not what Javascript designed to do. There is only a way to read browser setting from JS - using signed scripts.
I'm very experienced in C/C++/Objective-C and over the last few days have been trying my hand at html/css/JS and am finding it very frustrating.
Time and time and time again I've been caught out as I've a syntax error or undeclared variable due to copying / pasting etc. with the consequence being that the code suddenly stops working then I have to scratch my head and figure out why.
The most painful thing is resorting to sprinkling alerts in the code everything something fails in order to track down the reason. I know there is the new console object for logging but it doesn't seem to work with Komodoedit or jsFiddle? Which is what I've been using.
Is there a way of using these tool, or alternative tools where I can step through the code line by line in a debugger like I can with other languages? Or any tricks for easy detection of problems with the code before executing it in addition to jslint?
[I don't want to use any libraries that might have built-in support for logging etc. as I'm finding they (well JQuery/JQuery mobile is) are drastically slowing down loading times on an iPhone so want to concentrate on pure JS.]
[My target browser is just iOS, but am using Komodoedit with Chrome most of the time and every few hours try it on an iPhone]
Thanks
You need several tools.
First, get yourself a real debugger. I use the one built into Chrome. There's a similar one built into Safari and Firebug available as an add-on for Firefox. This will allow you to set breakpoints and step through your code and see exactly what is happening.
Second, get very used to running your code through jsLint. This will show you many obvious typos and encourage you to write robust code from day one.
Third, start writing in strict mode. This will again prevent some obvious typos and force you to start some good habits.
Fourth, use console.log() when needed. Once you have a debugger, it's output will show in the debug console of the debugger for any page in your browser, including jsFiddle pages. You will have to invoke the debugger on the right frame in jsFiddle and then it will work fine. I use both a regular debugger and console.log() all the time with jsFiddle. It takes a little figuring in jsFiddle and the debugger to find where your own code is to set breakpoints, but once you find it, it's easy to use.
Fifth, javascript is simply not C++. While the syntax will seem quite familiar, the way you do things with anonymous functions and closures and objects and prototypes is very different. As one who programmed in C++ for many, many years before learning javascript, I very much appreciate what I can do now in javascript that was a lot more work in C++, but it took awhile to get my brain into a new mode of thinking. I spent too much time in my first years of javascript development trying to emulate C++ techniques rather than just learning the better way to accomplish the goal in javascript.
Sixth, you will have to change how you write and test code because of the lack of a compiler that finds errors for you. I remember in the days of C++, when I needed to refactor something, I could make a bunch of changes and then let the compiler find all the other places I need to fix the syntax. You can't do that with javascript. When you make mass changes, you can run through jsLint to find some issues and then you literally need to execute every path to make sure everything works. It is a bit of a pain.
Seventh, find a strategy/tools for unit testing. Once a project gets more than a few functions long, you will benefit greatly from building unit tests that you can run anytime you make significant changes. They will both find issues for you in a lot less time than without the unit tests and they will give you the courage to refactor and clean up your code when you see the need for that because you know the unit tests will tell you if everything is working again. It's extra work up front that pays dividends many times over down the road.
Firefox has an add-on called FireBug that is very helpful for debugging CSS/javascript, and yes, it does have the ability to step through a script as well as a command line where you can try out various javascript expressions. I'm pretty sure Chrome has a similar feature.
Here is the article in which you get a list of tools to debug the javascript
advance-javascript-debugging-techniques
Since you're using Chrome, you just need to open the developer console (spanner -> tools -> javascript console, or Ctrl+Alt+J (at a guess)). Instead of sprinkling your code with alerts, use console.log, console.error, and console.info to print to it. All of those are variadic, so you can pass as much to one call as you need.
In addition to this, you can use the console to test and modify parts of your code on the fly, or to just try out a few snippets to see if they work. It's a fully functional REPL that also works with the current document.
In the sources tab of the developer console, you are able to set breakpoints and step through your code, analysing state at each point. This page goes into some detail about it: http://chromedevtools.googlecode.com/svn-history/r421/trunk/tutorials/breapoints/index.html
In the elements tab, you are able to set breakpoints on changes to elements in the DOM, including changes to attributes and child nodes. Right click a node and select the option you want. This will come in handy when debugging code that is asynchronous and plays with the document (eg. AJAX calls inserting new content).
In addition to this, you can scroll to the bottom of the styles pane to the right, and open the event listeners section. Here, you can inspect all the events bound to the selected DOM node.
You can enter debugger (without a semicolon) into your code, and it will open the sources tab at that point so you can inspect the code further. I think this may be Chrome specific.
Finally, tools like JSlint will help you spot undeclared variables as you code, as well as cases where the formatting of your code creates unexpected errors, and some might even go as far as using syntax highlighting to make you notice variables that are undefined.
This is also just scraping the surface. Your editor and JSlint can make your code look right and parse without error, but the browser and its console is where you will spend most of your time.
I am developing an application on Facebook. I am running into some vague situation that I want to debug. The problem is that Facebook adds MUCH wrapping code and changes the name, not to mention that it already uses a modified version of JavaScript called FBJS. These things make it almost impossible to use tools like FireBug to debug the code. Does anybody have a suggestion for such cases? I am thinking of some debugging library that traces the code, variables, etc., and show me some results in some other window, or something like that.
You can try adding the line debugger to your javascript where you want to break. Firebug should break point on that line.
Why some javascript error only comes in IE not in firefox? should i solve all IE javascript errors, if my site is working fine with it ?
You should definitely seek to fix any JS errors you are getting in IE. What shows up in your IE as a little yellow icon, will show up in other IE browsers as a popup letting the user know there was an error.
One way you can minimize problems is by using one of the many JavaScript framework/libraries like jQuery, MooTools, etc that seek to minimize browser differences. Then, when you get specific errors, they can often be fixed by added a missing ; or adding an if statement in the correct place.
You should never knowingly leave code unfixed that is known to break in modern browsers.
should i solve all IE javascript
errors, if my site is working fine
with it ?
I'd say, yes absolutely. Under certain circumstances, IE throws Javascript errors right into the user's face with a big fat dialog. I think it's very embarrassing for a visitor (who may not even know what JS is, and even less the intricacies of cross-browser scripting) to get a error message as their first impression of you.
they have slightly different implementations of javascript, dom, css, etc.... should you fix the errors? if no major functionality is impacted, then it would probably be a very low priority... and depending on your userbase (say its a corporate intranet) you could simply say Firefox is your preferred browser. all depends on the requirements. Prioritizing tasks will help ensure the most important objectives are met.
Yes, you should fix the Javascript errors being reported in IE, because it can be unclear how the errors manifest themselves in your application. For instance, it can cause menu navigation to not work, or incorrect behavior of buttons.
As for actually detecting where the problem came from and how to fix it, you can try our Browsera service, which will detect and log the Javascript errors for you that occur in the browser, and use the Script Editor, which comes with MS Office
Or, if you dont have OFfice, use the free Microsoft Script Debugger, which works, but is less powerful.
if you are working with ajax than you can use $.getJason using jQuery, instead you get data from ajax and then use JSON.parse();
Not sure if there is any Firefox add-on tool for checking JavaScript syntax, var declaration, or even pre-compiling available?
I find out is very difficult to debug JavaScript in a web html page. I have to add some script there. When the scripts get very big or long, it stops working. Basically, there must be some bugs. It is very frustrating even the load event stop working. I do need some good tools to find out the bugs.
I have tried FireBug. It is good but not enough. Maybe I don't know all its features. Anyway, I need any good suggestions.
This page may help you a bit as it also contains a screencast.
Debugging Javascript in Firefox with Firebug
It's not strictly an Add-On (although you can obviously run it in a Firefox web page), but I've found JSLint to be helpful in exposing expression anomalies that might or might not be strictly invalid syntax (although it will catch all those, too.)
My suggestion is to check you javascript with JSLint. JSLint will show you common problems in javascript code and helps you to create strict and compatible code.
YSlow includes JSLint as Tool.
As an alternative to FireBug check this debugger: Venkman JavaScript Debugger, has been out there for a while, and it's not bad at all...
I have always been a firebug fan and it sure is one of the best debuggers out there. Any JS issue Press F12, Enable the console for catching the errors and then you can find the exact line causing the error. Add a breakpoint and you can see the exact values of variables too. Very intuitive UI..just get used to using it and it will save a lot of your time.
I HIGHLY recommend Rainbow. It's still in Beta and only works in FF3, but it offers syntax highlighting. That will get you half-way there when it comes to syntax.
I constantly use firebug with a js file that has some 15000 lines. I've had no problems with it (sometimes I have to wait a few seconds for it to scroll to the breakpoint but even then it works fine).
Unfortunately JSLint does'nt work for us. We use some third party code that while beeing "valid" has unnecessary ";" according to jsLint. The code is in the beginning of our js file and jslint stops analyzing at 3% because it thinks there are too many errors (all of them unnecessary ";".)
You're missing the point on 2 counts:
First, being presented with a gazillion unnecessary error messages will make it impossible to find the problem in the first place.
Secondly, the errors are unnecessary. I used to use JSLint religiously, but now it's become too much of a code Nazi and I can't use it.
I'm aware that many of the things it checks for can be disabled, but I just don't have enough time to research what I'd have to do.
The issue is the usability of the default configuration. I, like the original poster, am just looking for a way to find true JavaScript syntax errors very quickly, including on HTML pages. I'm sure that Firebug can do it, but as in the case with JSLint, I don't have the spare time to find out how.
I do, however, use Firebug for debugging, though the version I'm using (1.10.3) has a bad habit of displaying errors, but reporting an incorrect file and line number.
Hi Gene: you could change one variable option.maxerr inside your jslint.js file into the number you want.
The default value is 50, you could change it to 500 or 1000 to suite your taste.
I use both the following for code validation.
JSHint # http://jshint.com
JSLint FF Plugin. Get at https://addons.mozilla.org/en-us/firefox/addon/jslinter/
Alternatively, jshint and jslint plugins are available for text editors like Notepad ++, sublime etc.