.config/coc/extensions/node_modules/coc-json/node_modules/debug/README.md

   1 # debug
   2 [![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)
   3 [![OpenCollective](https://opencollective.com/debug/sponsors/badge.svg)](#sponsors)
   4
   5 <img width="647" src="https://user-images.githubusercontent.com/71256/29091486-fa38524c-7c37-11e7-895f-e7ec8e1039b6.png">
   6
   7 A tiny JavaScript debugging utility modelled after Node.js core's debugging
   8 technique. Works in Node.js and web browsers.
   9
  10 ## Installation
  11
  12 ```bash
  13 $ npm install debug
  14 ```
  15
  16 ## Usage
  17
  18 `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.
  19
  20 Example [_app.js_](./examples/node/app.js):
  21
  22 ```js
  23 var debug = require('debug')('http')
  24   , http = require('http')
  25   , name = 'My App';
  26
  27 // fake app
  28
  29 debug('booting %o', name);
  30
  31 http.createServer(function(req, res){
  32   debug(req.method + ' ' + req.url);
  33   res.end('hello\n');
  34 }).listen(3000, function(){
  35   debug('listening');
  36 });
  37
  38 // fake worker of some kind
  39
  40 require('./worker');
  41 ```
  42
  43 Example [_worker.js_](./examples/node/worker.js):
  44
  45 ```js
  46 var a = require('debug')('worker:a')
  47   , b = require('debug')('worker:b');
  48
  49 function work() {
  50   a('doing lots of uninteresting work');
  51   setTimeout(work, Math.random() * 1000);
  52 }
  53
  54 work();
  55
  56 function workb() {
  57   b('doing some work');
  58   setTimeout(workb, Math.random() * 2000);
  59 }
  60
  61 workb();
  62 ```
  63
  64 The `DEBUG` environment variable is then used to enable these based on space or
  65 comma-delimited names.
  66
  67 Here are some examples:
  68
  69 <img width="647" alt="screen shot 2017-08-08 at 12 53 04 pm" src="https://user-images.githubusercontent.com/71256/29091703-a6302cdc-7c38-11e7-8304-7c0b3bc600cd.png">
  70 <img width="647" alt="screen shot 2017-08-08 at 12 53 38 pm" src="https://user-images.githubusercontent.com/71256/29091700-a62a6888-7c38-11e7-800b-db911291ca2b.png">
  71 <img width="647" alt="screen shot 2017-08-08 at 12 53 25 pm" src="https://user-images.githubusercontent.com/71256/29091701-a62ea114-7c38-11e7-826a-2692bedca740.png">
  72
  73 #### Windows note
  74
  75 On Windows the environment variable is set using the `set` command.
  76
  77 ```cmd
  78 set DEBUG=*,-not_this
  79 ```
  80
  81 Note that PowerShell uses different syntax to set environment variables.
  82
  83 ```cmd
  84 $env:DEBUG = "*,-not_this"
  85 ```
  86
  87 Then, run the program to be debugged as usual.
  88
  89
  90 ## Namespace Colors
  91
  92 Every debug instance has a color generated for it based on its namespace name.
  93 This helps when visually parsing the debug output to identify which debug instance
  94 a debug line belongs to.
  95
  96 #### Node.js
  97
  98 In Node.js, colors are enabled when stderr is a TTY. You also _should_ install
  99 the [`supports-color`](https://npmjs.org/supports-color) module alongside debug,
 100 otherwise debug will only use a small handful of basic colors.
 101
 102 <img width="521" src="https://user-images.githubusercontent.com/71256/29092181-47f6a9e6-7c3a-11e7-9a14-1928d8a711cd.png">
 103
 104 #### Web Browser
 105
 106 Colors are also enabled on "Web Inspectors" that understand the `%c` formatting
 107 option. These are WebKit web inspectors, Firefox ([since version
 108 31](https://hacks.mozilla.org/2014/05/editable-box-model-multiple-selection-sublime-text-keys-much-more-firefox-developer-tools-episode-31/))
 109 and the Firebug plugin for Firefox (any version).
 110
 111 <img width="524" src="https://user-images.githubusercontent.com/71256/29092033-b65f9f2e-7c39-11e7-8e32-f6f0d8e865c1.png">
 112
 113
 114 ## Millisecond diff
 115
 116 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.
 117
 118 <img width="647" src="https://user-images.githubusercontent.com/71256/29091486-fa38524c-7c37-11e7-895f-e7ec8e1039b6.png">
 119
 120 When stdout is not a TTY, `Date#toISOString()` is used, making it more useful for logging the debug information as shown below:
 121
 122 <img width="647" src="https://user-images.githubusercontent.com/71256/29091956-6bd78372-7c39-11e7-8c55-c948396d6edd.png">
 123
 124
 125 ## Conventions
 126
 127 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".  If you append a "*" to the end of your name, it will always be enabled regardless of the setting of the DEBUG environment variable.  You can then use it for normal output as well as debug output.
 128
 129 ## Wildcards
 130
 131 The `*` character may be used as a wildcard. Suppose for example your library has
 132 debuggers named "connect:bodyParser", "connect:compress", "connect:session",
 133 instead of listing all three with
 134 `DEBUG=connect:bodyParser,connect:compress,connect:session`, you may simply do
 135 `DEBUG=connect:*`, or to run everything using this module simply use `DEBUG=*`.
 136
 137 You can also exclude specific debuggers by prefixing them with a "-" character.
 138 For example, `DEBUG=*,-connect:*` would include all debuggers except those
 139 starting with "connect:".
 140
 141 ## Environment Variables
 142
 143 When running through Node.js, you can set a few environment variables that will
 144 change the behavior of the debug logging:
 145
 146 | Name      | Purpose                                         |
 147 |-----------|-------------------------------------------------|
 148 | `DEBUG`   | Enables/disables specific debugging namespaces. |
 149 | `DEBUG_HIDE_DATE` | Hide date from debug output (non-TTY).  |
 150 | `DEBUG_COLORS`| Whether or not to use colors in the debug output. |
 151 | `DEBUG_DEPTH` | Object inspection depth.                    |
 152 | `DEBUG_SHOW_HIDDEN` | Shows hidden properties on inspected objects. |
 153
 154
 155 __Note:__ The environment variables beginning with `DEBUG_` end up being
 156 converted into an Options object that gets used with `%o`/`%O` formatters.
 157 See the Node.js documentation for
 158 [`util.inspect()`](https://nodejs.org/api/util.html#util_util_inspect_object_options)
 159 for the complete list.
 160
 161 ## Formatters
 162
 163 Debug uses [printf-style](https://wikipedia.org/wiki/Printf_format_string) formatting.
 164 Below are the officially supported formatters:
 165
 166 | Formatter | Representation |
 167 |-----------|----------------|
 168 | `%O`      | Pretty-print an Object on multiple lines. |
 169 | `%o`      | Pretty-print an Object all on a single line. |
 170 | `%s`      | String. |
 171 | `%d`      | Number (both integer and float). |
 172 | `%j`      | JSON. Replaced with the string '[Circular]' if the argument contains circular references. |
 173 | `%%`      | Single percent sign ('%'). This does not consume an argument. |
 174
 175
 176 ### Custom formatters
 177
 178 You can add custom formatters by extending the `debug.formatters` object.
 179 For example, if you wanted to add support for rendering a Buffer as hex with
 180 `%h`, you could do something like:
 181
 182 ```js
 183 const createDebug = require('debug')
 184 createDebug.formatters.h = (v) => {
 185   return v.toString('hex')
 186 }
 187
 188 // …elsewhere
 189 const debug = createDebug('foo')
 190 debug('this is hex: %h', new Buffer('hello world'))
 191 //   foo this is hex: 68656c6c6f20776f726c6421 +0ms
 192 ```
 193
 194
 195 ## Browser Support
 196
 197 You can build a browser-ready script using [browserify](https://github.com/substack/node-browserify),
 198 or just use the [browserify-as-a-service](https://wzrd.in/) [build](https://wzrd.in/standalone/debug@latest),
 199 if you don't want to build it yourself.
 200
 201 Debug's enable state is currently persisted by `localStorage`.
 202 Consider the situation shown below where you have `worker:a` and `worker:b`,
 203 and wish to debug both. You can enable this using `localStorage.debug`:
 204
 205 ```js
 206 localStorage.debug = 'worker:*'
 207 ```
 208
 209 And then refresh the page.
 210
 211 ```js
 212 a = debug('worker:a');
 213 b = debug('worker:b');
 214
 215 setInterval(function(){
 216   a('doing some work');
 217 }, 1000);
 218
 219 setInterval(function(){
 220   b('doing some work');
 221 }, 1200);
 222 ```
 223
 224
 225 ## Output streams
 226
 227   By default `debug` will log to stderr, however this can be configured per-namespace by overriding the `log` method:
 228
 229 Example [_stdout.js_](./examples/node/stdout.js):
 230
 231 ```js
 232 var debug = require('debug');
 233 var error = debug('app:error');
 234
 235 // by default stderr is used
 236 error('goes to stderr!');
 237
 238 var log = debug('app:log');
 239 // set this namespace to log via console.log
 240 log.log = console.log.bind(console); // don't forget to bind to console!
 241 log('goes to stdout');
 242 error('still goes to stderr!');
 243
 244 // set all output to go via console.info
 245 // overrides all per-namespace log settings
 246 debug.log = console.info.bind(console);
 247 error('now goes to stdout via console.info');
 248 log('still goes to stdout, but via console.info now');
 249 ```
 250
 251 ## Checking whether a debug target is enabled
 252
 253 After you've created a debug instance, you can determine whether or not it is
 254 enabled by checking the `enabled` property:
 255
 256 ```javascript
 257 const debug = require('debug')('http');
 258
 259 if (debug.enabled) {
 260   // do stuff...
 261 }
 262 ```
 263
 264 You can also manually toggle this property to force the debug instance to be
 265 enabled or disabled.
 266
 267
 268 ## Authors
 269
 270  - TJ Holowaychuk
 271  - Nathan Rajlich
 272  - Andrew Rhyne
 273
 274 ## Backers
 275
 276 Support us with a monthly donation and help us continue our activities. [[Become a backer](https://opencollective.com/debug#backer)]
 277
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 308
 309
 310 ## Sponsors
 311
 312 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)]
 313
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 343 <a href="https://opencollective.com/debug/sponsor/29/website" target="_blank"><img src="https://opencollective.com/debug/sponsor/29/avatar.svg"></a>
 344
 345 ## License
 346
 347 (The MIT License)
 348
 349 Copyright (c) 2014-2017 TJ Holowaychuk &lt;tj@vision-media.ca&gt;
 350
 351 Permission is hereby granted, free of charge, to any person obtaining
 352 a copy of this software and associated documentation files (the
 353 'Software'), to deal in the Software without restriction, including
 354 without limitation the rights to use, copy, modify, merge, publish,
 355 distribute, sublicense, and/or sell copies of the Software, and to
 356 permit persons to whom the Software is furnished to do so, subject to
 357 the following conditions:
 358
 359 The above copyright notice and this permission notice shall be
 360 included in all copies or substantial portions of the Software.
 361
 362 THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
 363 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 364 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 365 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 366 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 367 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 368 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.