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tiny node.js debugging utility modelled after node core's debugging technique.

$ npm install debug

Withdebug you simply invoke the exported function to generate your debug function, passing it a name which will determine if a noop function is returned, or a decoratedconsole.error, so all of theconsole format string goodies you're used to work fine. A unique color is selected per-function for visibility.

Exampleapp.js:

vardebug=require('debug')('http'),http=require('http'),name='My App';// fake appdebug('booting %s',name);http.createServer(function(req,res){debug(req.method+' '+req.url);res.end('hello\n');}).listen(3000,function(){debug('listening');});// fake worker of some kindrequire('./worker');

Exampleworker.js:

vardebug=require('debug')('worker');setInterval(function(){debug('doing some work');},1000);

TheDEBUG environment variable is then used to enable these based on space or comma-delimited names. Here are some examples:

When actively developing an application it can be useful to see when the time spent between onedebug() call and the next. Suppose for example you invokedebug() before requesting a resource, and after as well, the "+NNNms" will show you how much time was spent between calls.

When stdout is not a TTY,Date#toUTCString() is used, making it more useful for logging the debug information as shown below:

If you're using this in one or more of your libraries, youshould use the name of your library so that developers may toggle debugging as desired without guessing names. If you have more than one debuggers youshould prefix them with your library name and use ":" to separate features. For example "bodyParser" from Connect would then be "connect:bodyParser".

The "*" character may be used as a wildcard. Suppose for example your library has debuggers named "connect:bodyParser", "connect:compress", "connect:session", instead of listing all three withDEBUG=connect:bodyParser,connect.compress,connect:session, you may simply doDEBUG=connect:*, or to run everything using this module simply useDEBUG=*.

You can also exclude specific debuggers by prefixing them with a "-" character. For example,DEBUG=* -connect:* would include all debuggers except those starting with "connect:".

Debug works in the browser as well, currently persisted bylocalStorage. For example if you haveworker:a andworker:b as shown below, and wish to debug both typedebug.enable('worker:*') in the console and refresh the page, this will remain until you disable withdebug.disable().

a=debug('worker:a');b=debug('worker:b');setInterval(function(){a('doing some work');},1000);setInterval(function(){a('doing some work');},1200);

(The MIT License)

Copyright (c) 2011 TJ Holowaychuk <tj@vision-media.ca>

Permission is hereby granted, free of charge, to any person obtaininga copy of this software and associated documentation files (the'Software'), to deal in the Software without restriction, includingwithout limitation the rights to use, copy, modify, merge, publish,distribute, sublicense, and/or sell copies of the Software, and topermit persons to whom the Software is furnished to do so, subject tothe following conditions:

The above copyright notice and this permission notice shall beincluded in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OFMERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANYCLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THESOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.