|
# debug |
|
[![Build Status](https://travis-ci.org/visionmedia/debug.svg?branch=master)](https://travis-ci.org/visionmedia/debug) [![Coverage Status](https://coveralls.io/repos/github/visionmedia/debug/badge.svg?branch=master)](https://coveralls.io/github/visionmedia/debug?branch=master) [![Slack](https://visionmedia-community-slackin.now.sh/badge.svg)](https://visionmedia-community-slackin.now.sh/) [![OpenCollective](https://opencollective.com/debug/backers/badge.svg)](#backers) |
|
[![OpenCollective](https://opencollective.com/debug/sponsors/badge.svg)](#sponsors) |
|
|
|
|
|
|
|
A tiny node.js debugging utility modelled after node core's debugging technique. |
|
|
|
**Discussion around the V3 API is under way [here](https://github.com/visionmedia/debug/issues/370)** |
|
|
|
## Installation |
|
|
|
```bash |
|
$ npm install debug |
|
``` |
|
|
|
## Usage |
|
|
|
`debug` exposes a function; simply pass this function the name of your module, and it will return a decorated version of `console.error` for you to pass debug statements to. This will allow you to toggle the debug output for different parts of your module as well as the module as a whole. |
|
|
|
Example _app.js_: |
|
|
|
```js |
|
var debug = require('debug')('http') |
|
, http = require('http') |
|
, name = 'My App'; |
|
|
|
// fake app |
|
|
|
debug('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 kind |
|
|
|
require('./worker'); |
|
``` |
|
|
|
Example _worker.js_: |
|
|
|
```js |
|
var debug = require('debug')('worker'); |
|
|
|
setInterval(function(){ |
|
debug('doing some work'); |
|
}, 1000); |
|
``` |
|
|
|
The __DEBUG__ environment variable is then used to enable these based on space or comma-delimited names. Here are some examples: |
|
|
|
![debug http and worker](http://f.cl.ly/items/18471z1H402O24072r1J/Screenshot.png) |
|
|
|
![debug worker](http://f.cl.ly/items/1X413v1a3M0d3C2c1E0i/Screenshot.png) |
|
|
|
#### Windows note |
|
|
|
On Windows the environment variable is set using the `set` command. |
|
|
|
```cmd |
|
set DEBUG=*,-not_this |
|
``` |
|
|
|
Note that PowerShell uses different syntax to set environment variables. |
|
|
|
```cmd |
|
$env:DEBUG = "*,-not_this" |
|
``` |
|
|
|
Then, run the program to be debugged as usual. |
|
|
|
## Millisecond diff |
|
|
|
When actively developing an application it can be useful to see when the time spent between one `debug()` call and the next. Suppose for example you invoke `debug()` before requesting a resource, and after as well, the "+NNNms" will show you how much time was spent between calls. |
|
|
|
![](http://f.cl.ly/items/2i3h1d3t121M2Z1A3Q0N/Screenshot.png) |
|
|
|
When stdout is not a TTY, `Date#toUTCString()` is used, making it more useful for logging the debug information as shown below: |
|
|
|
![](http://f.cl.ly/items/112H3i0e0o0P0a2Q2r11/Screenshot.png) |
|
|
|
## Conventions |
|
|
|
If you're using this in one or more of your libraries, you _should_ use the name of your library so that developers may toggle debugging as desired without guessing names. If you have more than one debuggers you _should_ prefix them with your library name and use ":" to separate features. For example "bodyParser" from Connect would then be "connect:bodyParser". |
|
|
|
## Wildcards |
|
|
|
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 with `DEBUG=connect:bodyParser,connect:compress,connect:session`, you may simply do `DEBUG=connect:*`, or to run everything using this module simply use `DEBUG=*`. |
|
|
|
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:". |
|
|
|
## Environment Variables |
|
|
|
When running through Node.js, you can set a few environment variables that will |
|
change the behavior of the debug logging: |
|
|
|
| Name | Purpose | |
|
|-----------|-------------------------------------------------| |
|
| `DEBUG` | Enables/disables specific debugging namespaces. | |
|
| `DEBUG_COLORS`| Whether or not to use colors in the debug output. | |
|
| `DEBUG_DEPTH` | Object inspection depth. | |
|
| `DEBUG_SHOW_HIDDEN` | Shows hidden properties on inspected objects. | |
|
|
|
|
|
__Note:__ The environment variables beginning with `DEBUG_` end up being |
|
converted into an Options object that gets used with `%o`/`%O` formatters. |
|
See the Node.js documentation for |
|
[`util.inspect()`](https://nodejs.org/api/util.html#util_util_inspect_object_options) |
|
for the complete list. |
|
|
|
## Formatters |
|
|
|
|
|
Debug uses [printf-style](https://wikipedia.org/wiki/Printf_format_string) formatting. Below are the officially supported formatters: |
|
|
|
| Formatter | Representation | |
|
|-----------|----------------| |
|
| `%O` | Pretty-print an Object on multiple lines. | |
|
| `%o` | Pretty-print an Object all on a single line. | |
|
| `%s` | String. | |
|
| `%d` | Number (both integer and float). | |
|
| `%j` | JSON. Replaced with the string '[Circular]' if the argument contains circular references. | |
|
| `%%` | Single percent sign ('%'). This does not consume an argument. | |
|
|
|
### Custom formatters |
|
|
|
You can add custom formatters by extending the `debug.formatters` object. For example, if you wanted to add support for rendering a Buffer as hex with `%h`, you could do something like: |
|
|
|
```js |
|
const createDebug = require('debug') |
|
createDebug.formatters.h = (v) => { |
|
return v.toString('hex') |
|
} |
|
|
|
// …elsewhere |
|
const debug = createDebug('foo') |
|
debug('this is hex: %h', new Buffer('hello world')) |
|
// foo this is hex: 68656c6c6f20776f726c6421 +0ms |
|
``` |
|
|
|
## Browser support |
|
You can build a browser-ready script using [browserify](https://github.com/substack/node-browserify), |
|
or just use the [browserify-as-a-service](https://wzrd.in/) [build](https://wzrd.in/standalone/debug@latest), |
|
if you don't want to build it yourself. |
|
|
|
Debug's enable state is currently persisted by `localStorage`. |
|
Consider the situation shown below where you have `worker:a` and `worker:b`, |
|
and wish to debug both. You can enable this using `localStorage.debug`: |
|
|
|
```js |
|
localStorage.debug = 'worker:*' |
|
``` |
|
|
|
And then refresh the page. |
|
|
|
```js |
|
a = debug('worker:a'); |
|
b = debug('worker:b'); |
|
|
|
setInterval(function(){ |
|
a('doing some work'); |
|
}, 1000); |
|
|
|
setInterval(function(){ |
|
b('doing some work'); |
|
}, 1200); |
|
``` |
|
|
|
#### Web Inspector Colors |
|
|
|
Colors are also enabled on "Web Inspectors" that understand the `%c` formatting |
|
option. These are WebKit web inspectors, Firefox ([since version |
|
31](https://hacks.mozilla.org/2014/05/editable-box-model-multiple-selection-sublime-text-keys-much-more-firefox-developer-tools-episode-31/)) |
|
and the Firebug plugin for Firefox (any version). |
|
|
|
Colored output looks something like: |
|
|
|
![](https://cloud.githubusercontent.com/assets/71256/3139768/b98c5fd8-e8ef-11e3-862a-f7253b6f47c6.png) |
|
|
|
|
|
## Output streams |
|
|
|
By default `debug` will log to stderr, however this can be configured per-namespace by overriding the `log` method: |
|
|
|
Example _stdout.js_: |
|
|
|
```js |
|
var debug = require('debug'); |
|
var error = debug('app:error'); |
|
|
|
// by default stderr is used |
|
error('goes to stderr!'); |
|
|
|
var log = debug('app:log'); |
|
// set this namespace to log via console.log |
|
log.log = console.log.bind(console); // don't forget to bind to console! |
|
log('goes to stdout'); |
|
error('still goes to stderr!'); |
|
|
|
// set all output to go via console.info |
|
// overrides all per-namespace log settings |
|
debug.log = console.info.bind(console); |
|
error('now goes to stdout via console.info'); |
|
log('still goes to stdout, but via console.info now'); |
|
``` |
|
|
|
|
|
## Authors |
|
|
|
- TJ Holowaychuk |
|
- Nathan Rajlich |
|
- Andrew Rhyne |
|
|
|
## Backers |
|
|
|
Support us with a monthly donation and help us continue our activities. [[Become a backer](https://opencollective.com/debug#backer)] |
|
|
|
<a href="https://opencollective.com/debug/backer/0/website" target="_blank"><img src="https://opencollective.com/debug/backer/0/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/1/website" target="_blank"><img src="https://opencollective.com/debug/backer/1/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/2/website" target="_blank"><img src="https://opencollective.com/debug/backer/2/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/3/website" target="_blank"><img src="https://opencollective.com/debug/backer/3/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/4/website" target="_blank"><img src="https://opencollective.com/debug/backer/4/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/5/website" target="_blank"><img src="https://opencollective.com/debug/backer/5/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/6/website" target="_blank"><img src="https://opencollective.com/debug/backer/6/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/7/website" target="_blank"><img src="https://opencollective.com/debug/backer/7/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/8/website" target="_blank"><img src="https://opencollective.com/debug/backer/8/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/9/website" target="_blank"><img src="https://opencollective.com/debug/backer/9/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/10/website" target="_blank"><img src="https://opencollective.com/debug/backer/10/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/11/website" target="_blank"><img src="https://opencollective.com/debug/backer/11/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/12/website" target="_blank"><img src="https://opencollective.com/debug/backer/12/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/13/website" target="_blank"><img src="https://opencollective.com/debug/backer/13/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/14/website" target="_blank"><img src="https://opencollective.com/debug/backer/14/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/15/website" target="_blank"><img src="https://opencollective.com/debug/backer/15/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/16/website" target="_blank"><img src="https://opencollective.com/debug/backer/16/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/17/website" target="_blank"><img src="https://opencollective.com/debug/backer/17/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/18/website" target="_blank"><img src="https://opencollective.com/debug/backer/18/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/19/website" target="_blank"><img src="https://opencollective.com/debug/backer/19/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/20/website" target="_blank"><img src="https://opencollective.com/debug/backer/20/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/21/website" target="_blank"><img src="https://opencollective.com/debug/backer/21/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/22/website" target="_blank"><img src="https://opencollective.com/debug/backer/22/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/23/website" target="_blank"><img src="https://opencollective.com/debug/backer/23/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/24/website" target="_blank"><img src="https://opencollective.com/debug/backer/24/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/25/website" target="_blank"><img src="https://opencollective.com/debug/backer/25/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/26/website" target="_blank"><img src="https://opencollective.com/debug/backer/26/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/27/website" target="_blank"><img src="https://opencollective.com/debug/backer/27/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/28/website" target="_blank"><img src="https://opencollective.com/debug/backer/28/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/backer/29/website" target="_blank"><img src="https://opencollective.com/debug/backer/29/avatar.svg"></a> |
|
|
|
|
|
## Sponsors |
|
|
|
Become a sponsor and get your logo on our README on Github with a link to your site. [[Become a sponsor](https://opencollective.com/debug#sponsor)] |
|
|
|
<a href="https://opencollective.com/debug/sponsor/0/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/0/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/1/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/1/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/2/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/2/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/3/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/3/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/4/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/4/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/5/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/5/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/6/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/6/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/7/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/7/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/8/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/8/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/9/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/9/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/10/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/10/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/11/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/11/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/12/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/12/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/13/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/13/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/14/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/14/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/15/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/15/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/16/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/16/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/17/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/17/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/18/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/18/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/19/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/19/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/20/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/20/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/21/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/21/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/22/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/22/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/23/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/23/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/24/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/24/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/25/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/25/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/26/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/26/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/27/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/27/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/28/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/28/avatar.svg"></a> |
|
<a href="https://opencollective.com/debug/sponsor/29/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/29/avatar.svg"></a> |
|
|
|
## License |
|
|
|
(The MIT License) |
|
|
|
Copyright (c) 2014-2016 TJ Holowaychuk <[email protected]> |
|
|
|
Permission is hereby granted, free of charge, to any person obtaining |
|
a copy of this software and associated documentation files (the |
|
'Software'), to deal in the Software without restriction, including |
|
without limitation the rights to use, copy, modify, merge, publish, |
|
distribute, sublicense, and/or sell copies of the Software, and to |
|
permit persons to whom the Software is furnished to do so, subject to |
|
the following conditions: |
|
|
|
The above copyright notice and this permission notice shall be |
|
included 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 OF |
|
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
|
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY |
|
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, |
|
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE |
|
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
|
|