by latentflip

latentflip / bows

Safe, production happy, colourful logging for chrome & firefox - makes reading your logs much easier...

211 Stars 21 Forks Last release: 12 months ago (v1.7.2) 185 Commits 34 Releases

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Colors Safe, production happy, colourful logging - makes reading your logs much easier.

(Rain)bows makes logging debug messages in your apps much nicer. - It allows you to create custom loggers for each module in your app, that prefix all log messages with the name of the app, so that you can scan the messages more easily. - It colors the prefix differently and distinctly for each logger/module so that it's even easier to read. - It can be safely used in production, where logging will be disabled by default, so that you can leave log messages in your code. - Loggers safely wrap console.log, to maintain the line number from where they are called in the console output.

Example Output


If you are using browserify, you'll want something like:

npm install bows --save

If you use Bower:

bower install bows --save

Otherwise, download either bows.js or bows.min.js.


  • Easily create prefixes for your logs, so that you can distinguish between logs from different parts of your app easily.
  • If supported, prefixes will be color coded for even easier identification.
  • Can be safely used in production, as logs will be disabled for your users, but can be enabled by you with a local storage flag.
  • Greppable logs by setting
    localStorage.debug = /Foo/
    to only display logs for modules matching the regex to help you focus in development.
    • Invert regex to remove logs matching with:
      localStorage.debug ='!/Foo/
  • Customize the localStorage key by setting
    and you can use
    to set your log grepping.

Browser Support

  • Works in all reasonable browsers
  • Supports colors in chrome, opera, firefox >= 31.0, electron


  • Works great in browserify and the browser.
  • Creating a new logger:
    • Browserify:
      var log = require('bows')("My Module Name")
    • Browser:
      var log = bows("My Module Name")
  • Then using it is easy:
    • log("Module loaded") //-> "My Module Name | Module Loaded"
    • log("Did something") //-> "My Module Name | Did something"
  • Typically each seperate module/view/etc in your app would create it's own logger. It will be assigned it's own color to make it easy to spot logs from different modules.
  • You can pass additional arguments to

    which will be automatically prepended to each message, e.g.:
    var log = bows("My App", "[ChuckNorris]");
    log("Kicks ass!");
    //My App         | [ChuckNorris] Kicks ass!
  • Logging is disabled by default. To enable logging, set

    localStorage.debug = true
    in your console and refresh the page.
  • To disable logging again, you must do

    delete localStorage.debug
    localStorage.debug = false
    will not work).
  • You can leave the code in in production, and log() will just safely no-op unless localStorage.debug is set.

  • Where colors are not supported, bows will just log plain text, but still with the module prefix.

    • If you wish to manually disable colors in an environment because detection is incorrect, set
      localStorage.debugColors = false
      , to reenable
      delete localStorage.debugColors


  //Should be set in your console to see messages
  localStorage.debug = true
  //Configure the max length of module names (optional)
  bows.config({ padLength: 10 })

var logger1 = bows('Module 1') var logger2 = bows('Module 2') var logger3 = bows('Module 3')

logger1("We started up") logger2("We did something too") logger3("I'm here") logger3("I'm still here") logger2("I'm tired") logger1("We're done here")


Example Output


Status: Build Status

This project uses

for tests. To run the tests install the development dependencies and then run:
npm test

New tests

Add a file in

, refer to enabled.html/disabled.html, then add the script to the array in test/index.js.

License & Credits


Copyright @philip_roberts /

With contributions from: * @lloydwatkin. * @camillereynders.

Bows depends on andlog, a nice little logging module by @HenrikJoreteg.


Please feel free to raise issues, or make contributions:

git clone
cd bows
npm install #install dependencies
#edit bows.js
npm test
npm run build.js #build dist/bows.js and dist/bows.min.js, also done by `npm test`

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