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
    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...

  • By
    CSS Filters

    CSS filter support recently landed within WebKit nightlies. CSS filters provide a method for modifying the rendering of a basic DOM element, image, or video. CSS filters allow for blurring, warping, and modifying the color intensity of elements. Let's have...

Incredible Demos

  • By
    HTML5 Input Types Alternative

    As you may know, HTML5 has introduced several new input types: number, date, color, range, etc. The question is: should you start using these controls or not? As much as I want to say "Yes", I think they are not yet ready for any real life...

  • By
    CSS Fixed Position Background Image

    Backgrounds have become an integral part of creating a web 2.0-esque website since gradients have become all the rage. If you think gradient backgrounds are too cliche, maybe a fixed position background would work for you? It does provide a neat inherent effect by...

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!