Force Stack Traces with JavaScript

By  on  

I recently inherited a Node.js project and man is that scary.  The code was well written but whenever you inherit a project you instantly inherit the fear of messing things up.  My goal was to fix a fairly routine bug, and finding the issue was fairly easy, but tracing through the code to figure out what called what and what passed what was a nightmare.

So I did the only thing I could do to figure out WTF was going on:

// The magic
console.log(new Error().stack);

/* SAMPLE:

Error
    at Object.module.exports.request (/home/vagrant/src/kumascript/lib/kumascript/caching.js:366:17)
    at attempt (/home/vagrant/src/kumascript/lib/kumascript/loaders.js:180:24)
    at ks_utils.Class.get (/home/vagrant/src/kumascript/lib/kumascript/loaders.js:194:9)
    at /home/vagrant/src/kumascript/lib/kumascript/macros.js:282:24
    at /home/vagrant/src/kumascript/node_modules/async/lib/async.js:118:13
    at Array.forEach (native)
    at _each (/home/vagrant/src/kumascript/node_modules/async/lib/async.js:39:24)
    at Object.async.each (/home/vagrant/src/kumascript/node_modules/async/lib/async.js:117:9)
    at ks_utils.Class.reloadTemplates (/home/vagrant/src/kumascript/lib/kumascript/macros.js:281:19)
    at ks_utils.Class.process (/home/vagrant/src/kumascript/lib/kumascript/macros.js:217:15)
*/

Of course the actual "error" doesn't matter -- the stack trace is exactly what you need to figure out what's calling what up the chain. When available you can also use console.trace() (when available) to achieve roughly the same output.  You can thank me later!

Recent Features

  • By
    Write Simple, Elegant and Maintainable Media Queries with Sass

    I spent a few months experimenting with different approaches for writing simple, elegant and maintainable media queries with Sass. Each solution had something that I really liked, but I couldn't find one that covered everything I needed to do, so I ventured into creating my...

  • By
    How I Stopped WordPress Comment Spam

    I love almost every part of being a tech blogger:  learning, preaching, bantering, researching.  The one part about blogging that I absolutely loathe:  dealing with SPAM comments.  For the past two years, my blog has registered 8,000+ SPAM comments per day.  PER DAY.  Bloating my database...

Incredible Demos

  • By
    Element Position Swapping Using MooTools 1.2

    We all know that MooTools 1.2 can do some pretty awesome animations. What if we want to quickly make two element swap positions without a lot of fuss? Now you can by implementing a MooTools swap() method. MooTools 1.2 Implementation MooTools 1.2 Usage To call the swap...

  • By
    Animated AJAX Record Deletion Using MooTools

    I'm a huge fan of WordPress' method of individual article deletion. You click the delete link, the menu item animates red, and the item disappears. Here's how to achieve that functionality with MooTools JavaScript. The PHP - Content & Header The following snippet goes at the...

Discussion

  1. Roman

    How about console.trace()?

    • console.trace() doesn’t exist on Chrome on Android.

  2. MaxArt

    How about node-inspector? It lets you use Chrome’s developer tools (sort of) to set breakpoints and inspect the code.
    I’m not debugging any node project without it anymore!

  3. Stuart

    Linked from JavaScript Daily. You can also use node debug whatever.js and put a debugger; statement in the location you want to inspect. Then the bt command will give you the trace.

  4. This is the solution I always use on my apps:

    https://gist.github.com/Venerons/f54b7fbc17f9df4302cf

    You can’t have more info than this. Really.

  5. Loupax

    I used to just call an undefined function in order to make an error appear. Lazy means to the same end I’d say

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!