Node.js Debugging

By  on  

Proper logging is of massive utility for web apps, both during development and after deployment.  What can sometimes be difficult is organizing both the code and output of logging, i.e. knowing where each log message is coming from.  I recently found debug, a Node.js utility for organized and optimized debugging.

Creating an instance of debug is simple and you can create multiple loggers per file:

// Create multiple instances of debug
// In theory these would serve two different purposes
var debuggerA = require('debug')('worker:a'),
    debuggerB = require('debug')('worker:b');

// Sample usages of the debugger
function work() {
  debuggerA('doing lots of uninteresting work');
  setTimeout(work, Math.random() * 1000);
}

work();

function workb() {
  debuggerB('doing some work');
  setTimeout(workb, Math.random() * 2000);
}

workb();

Node.js Debug

The namespace given to a debug instance as you must use an environment variable to signal which loggers should go to STDOUT when the script is run:

// Show all debugger messages prefixed "worker:_____"
DEBUG=worker:* node app.js

The environment variable strategy for signaling which instances should output is brilliant as you may want only certain types of messages logged in production vs. development.  Use namespaces wisely!

I was also able to use chalk to color messages as desired:

var chalk = require('chalk');

debuggerA(chalk.red.bold('OMG an awful error!'));

debug is one of those utilities that has a very simple purpose and accomplishes the task well.  Don't skimp when it comes to logging informative messages -- they'll help you during development and could be critical when auditing the app after a security incident!

Recent Features

  • By
    Facebook Open Graph META Tags

    It's no secret that Facebook has become a major traffic driver for all types of websites.  Nowadays even large corporations steer consumers toward their Facebook pages instead of the corporate websites directly.  And of course there are Facebook "Like" and "Recommend" widgets on every website.  One...

  • By
    CSS vs. JS Animation: Which is Faster?

    How is it possible that JavaScript-based animation has secretly always been as fast — or faster — than CSS transitions? And, how is it possible that Adobe and Google consistently release media-rich mobile sites that rival the performance of native apps? This article serves as a point-by-point...

Incredible Demos

  • By
    MooTools: Set Style Per Media

    I'd bet one of the most used MooTools methods is the setStyle() method, which allows you to set CSS style declarations for an element. One of the limitations of MooTools' setStyle() method is that it sets the specific style for all medias.

  • By
    Create Twitter-Style Dropdowns Using MooTools

    Twitter does some great stuff with JavaScript. What I really appreciate about what they do is that there aren't any epic JS functionalities -- they're all simple touches. One of those simple touches is the "Login" dropdown on their homepage. I've taken...

Discussion

  1. Allain

    Thanks for making this known. I’m pretty sure debug logs to STDERR so that piping still works.

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