Debug-Npm

https://www.npmjs.com/package/debug

2018.1.18 星期四 17:20

一 Install

$ npm install debug

二 Usage

2.1

var debug = require('debug')('http')
http = require('http')

debug('listening');

var a = require('debug')('worker:a')
    , b = require('debug')('worker:b');

function work() {
    a('doing lots of uninteresting work');
    setTimeout(work, Math.random() * 1000);
}

2.2 Windows

set DEBUG=*,-not_this

三 Namespace Colors

3.1 Node.js

colors are enabled when stderr is a TTY.
install the supports-color module alongside debug
// Question:?TTF

3.2 Web Browser

四 Millisecond diff

When stdout is not a TTY, Date#toISOString() is used
// Question:?TTF

五 Conventions

（公约、惯例、常规、etc）

六 Wildcards

（通配符） * -

七 Environment Variables

name	purpose
DEBUG	Enables/disables specific debugging namespaces.
DEBUG_HIDE_DATE	Hide date from debug output (non-TTY).
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.

八 Formatters

8.1

Debug uses printf-style 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.

8.2 Custom formatters

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

九 Browser Support

You can build a browser-ready script using browserify, or just use the browserify-as-a-service build, if you don’t want to build it yourself.

localStorage.debug = 'worker:*'
a = debug('worker:a');

十 Output streams

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');

// TODO:目前，尚不清楚，没有那么复杂的应用

一 Checking whether a debug target is enabled

const debug = require('debug')('http');
if (debug.enabled) {
    // do stuff...
}

Authors

Backers

License

(The MIT License)

17:50

学习总结：
快速学习，能够马上入手。
文档也就一页。
如需要深度掌握（有实际需求）再来学习