Package Exports

loglevel-plugin-prefix
loglevel-plugin-prefix/lib/loglevel-plugin-prefix

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (loglevel-plugin-prefix) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

loglevel-plugin-prefix

Plugin for loglevel message prefixing

Installation

npm install loglevel-plugin-prefix --save

API

apply(log[, options]);

This method applies the plugin to the logger.

log - loglevel logger

options - configuration object

var defaults = {
  template: '[%t] %l:',
  timestampFormatter: function (date) {
    return date.toTimeString().replace(/.*(\d{2}:\d{2}:\d{2}).*/, '$1');
  },
  levelFormatter: function (level) {
    return level.toUpperCase();
  },
  nameFormatter: function (name) {
    return name || 'root';
  }
};

Plugin formats the prefix using template option as a printf-like format.

The template is a string containing zero or more placeholder tokens. Each placeholder token is replaced with the value from loglevel messages parameters. Supported placeholders are:

%t - timestamp of message
%l - level of message
%n - name of logger

The timestampFormatter, levelFormatter and nameFormatter is a functions for formatting corresponding values

Base usage

Browser directly

<script src="https://unpkg.com/loglevel/dist/loglevel.min.js"></script>
<script src="https://unpkg.com/loglevel-plugin-prefix/dist/loglevel-plugin-prefix.min.js"></script>

<script>
  var logger = log.noConflict();
  var prefixer = prefix.noConflict();
  prefixer.apply(logger);
  logger.warn('prefixed message');
</script>

Output

[16:53:46] WARN: prefixed message

ES6

import log from 'loglevel';
import prefix from 'loglevel-plugin-prefix';

prefix.apply(log);
log.warn('prefixed message');

CommonJS

var log = require('loglevel');
var prefix = require('loglevel-plugin-prefix');

prefix.apply(log);
log.warn('prefixed message');

AMD

define(['loglevel', 'loglevel-plugin-prefix'], function(log, prefix) {
  prefix.apply(log);
  log.warn('prefixed message');
});

Custom options

var log = require('loglevel');
var prefix = require('loglevel-plugin-prefix');

prefix.apply(log, {
  template: '[%t] %l (%n) static text:',
  timestampFormatter: function (date) { return date.toISOString() },
  levelFormatter: function (level) { return level.charAt(0).toUpperCase() + level.substr(1) },
  nameFormatter: function (name) { return name || 'global' }
});

log.warn('prefixed message');

Output

[2017-05-29T12:53:46.000Z] Warn (global) static text: prefixed message

Example

// moduleA.js
var log = require('loglevel');

module.exports = function () {
  log.warn('message from moduleA');
}

// moduleB.js
var log = require('loglevel');

var logger = log.getLogger('moduleB');

module.exports = function () {
  logger.warn('message from moduleB');
}

// moduleC.js
var log = require('loglevel');

module.exports = function () {
  var logger = log.getLogger('moduleC');
  logger.warn('message from moduleC');
}

// main.js
var log = require('loglevel');
var prefix = require('loglevel-plugin-prefix');

var a = require('./moduleA');
var b = require('./moduleB');
var c = require('./moduleC');

log.warn('message from root %s prefixing', 'before');

prefix.apply(log, { template: '[%t] %l (%n):' });

log.warn('message from root %s prefixing', 'after');

a();
b();
c();

prefix.apply(log, {
  template: '[%t] %l:',
  timestampFormatter: function (date) { return date.toISOString() }
});

log.warn('message from root after reapplying');

Output

message from root before prefixing
[16:53:46] WARN (root): message from root after prefixing
[16:53:46] WARN (root): message from moduleA
message from moduleB
[16:53:46] WARN (moduleC): message from moduleC
[2017-05-29T12:53:46.000Z] WARN: message from root after reapplying