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I'm currently (trying) to develop an app with Worklight Studio 5.0.6 and Dojo (Mobile) 1.8.3. I have a really hard time to to find a proper method for debugging. After waiting 5-10 minutes for the build an deploy-process on the server, an error usually looks like this in the Chrome debugger:

enter image description here

How am I supposed to track down this error in MY source? The whole stack trace consists entirely of Dojo code which generates an absolutely useless error message after 20 abstraction layers.

Seriously, how do you guys handle this in real life? What methods do you use for debugging Dojo-driven apps in the browser?

spyro

some
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spyro
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    Did you provide `isDebug: true` in your `dojoConfig`? Also, try to see if the same occurs in other browsers. I have no clue why, but sometimes other browsers provide me with more information. – g00glen00b Oct 01 '13 at 17:24

4 Answers4

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For dojo.parse errors, I find it useful to pause the Chrome debugger on all exceptions (the purple icon on your screenshot, should be blue). You usally get more details about the cause of the error, the name of the DOM node being parsed, etc. in the first exception being raised.

Rémi.

Rémi Svahn
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Debugging dojo based application should be the same as debugging any javascript application.

Usually I will follow these steps:

  1. add console.log() somewhere in code: this is fast and most of time this is enough.

  2. set breakpoint in debugger: if step 1 is not enough, you can base on error information to set breakpoint before error line, then step in or step out.

  3. comment out recently changes: for some error which is hard to find the error line, for example, parse error in your case, the good way is comment out your recently changes one by one till back to your last working version. Or, return to your last working version, then add code back one by one.

  4. Create a simple application to reproduce the error : if your application is very complicate and it is hard for you to follow above methods, you can try to create a new application which mimics your current application but with simple logics and try to reproduce the error.

  5. Based on experience : Some errors, for example, extra ',' in the end of array which works at chrome and firefox, will report a nonsense error information at IE. Debug these kinds of errors is very difficult, you can base on your experience or do a google search.

Sean Zhao
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    Thanks for your answer, but all this is not really specific for Dojo with it's extensive use of callbacks and asynchronous AMD-Code where you simply don't know what actually caused the error (because your "class" is not part of the stack trace). It's not even possible to manipulate your page from the javascript console because of all the missing requirements. – spyro Oct 01 '13 at 14:24
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Did you provide isDebug: true in your dojoConfig? Also, try to see if the same occurs in other browsers.

Update: I recently discovered that there are issues with Google Chrome and Dojo debugging and I think it has to do with the asynchronous loading of files. As you can see in the provided screenshot of @spyro, the ReferenceError object is blank (which you can notice because of the empty brackets {}). If you want to solve that, reopen the console of Google Chrome, (for example by tapping F12 twice). After reopening the ReferenceError should not be empty anymore and now you can expand that object by using the arrow next to it and get a more detailed message about what failed.

g00glen00b
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Usually what I do in situations like that is to place a breakpoint inside the error callback (line 3398 in your case) and then look into the error variable ("e").

I am not sure how familiar you are with the Web Inspector, but once you hit the breakpoint open the Web Inspector 'console' and check for the error properties "e.message" and "e.stack" (just type in "e.message " in the console). Also, during development it is better to avoid Dojo optimization / minification, which greatly improve your debug-ability.

Bottom line is to try to place the breakpoint before the error is thrown.

eabe
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