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
    Chris Coyier’s Favorite CodePen Demos

    David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...

  • By
    6 Things You Didn’t Know About Firefox OS

    Firefox OS is all over the tech news and for good reason:  Mozilla's finally given web developers the platform that they need to create apps the way they've been creating them for years -- with CSS, HTML, and JavaScript.  Firefox OS has been rapidly improving...

Incredible Demos

  • By
    MooTools Star Ratings with MooStarRating

    I've said it over and over but I'll say it again:  JavaScript's main role in web applications is to enhance otherwise boring, static functionality provided by the browser.  One perfect example of this is the Javascript/AJAX-powered star rating systems that have become popular over the...

  • By
    GitHub-Style Sliding Links

    GitHub seems to change a lot but not really change at all, if that makes any sense; the updates come often but are always fairly small. I spotted one of the most recent updates on the pull request page. Links to long branch...

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!