loglevel-plugin-prefix
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    0.8.4 • Public • Published

    loglevel-plugin-prefix

    Plugin for loglevel message prefixing.

    NPM versionBuild Status

    Installation

    npm install loglevel-plugin-prefix

    API

    This plugin is under active development and should be considered as an unstable. No guarantees regarding API stability are made. Backward compatibility is guaranteed only by path releases.

    reg(loglevel)

    This method registers plugin for loglevel. This method must be called at least once before any call to the apply method. Repeated calls to this method are ignored.

    Parameters

    loglevel - the root logger, imported from loglevel module

    apply(logger, options)

    This method applies the plugin to the logger. Before using this method, the reg method must be called, otherwise a warning will be logged. From the next release, the call apply before reg will throw an error.

    Parameters

    logger - any logger of loglevel

    options - an optional configuration object

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

    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:

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

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

    Alternatively, you can use format option. This is a function that receives formatted values (level, name, timestamp) and should returns a prefix string.

    If both format andtemplate are present in the configuration, the template parameter is ignored. When both these parameters are missing in the configuration, the inherited behavior is used.

    Usage

    Browser directly

    <script src="https://unpkg.com/loglevel/dist/loglevel.min.js"></script>
    <script src="https://unpkg.com/loglevel-plugin-prefix@^0.8/dist/loglevel-plugin-prefix.min.js"></script>
     
    <script>
      var logger = log.noConflict();
      var prefixer = prefix.noConflict();
      prefixer.reg(logger);
      prefixer.apply(logger);
      logger.warn('prefixed message');
    </script> 

    Output

    [16:53:46] WARN: prefixed message
    

    Node

    const chalk = require('chalk');
    const log = require('loglevel');
    const prefix = require('loglevel-plugin-prefix');
     
    const colors = {
      TRACE: chalk.magenta,
      DEBUG: chalk.cyan,
      INFO: chalk.blue,
      WARN: chalk.yellow,
      ERROR: chalk.red,
    };
     
    prefix.reg(log);
    log.enableAll();
     
    prefix.apply(log, {
      format(level, name, timestamp) {
        return `${chalk.gray(`[${timestamp}]`)} ${colors[level.toUpperCase()](level)} ${chalk.green(`${name}:`)}`;
      },
    });
     
    prefix.apply(log.getLogger('critical'), {
      format(level, name, timestamp) {
        return chalk.red.bold(`[${timestamp}${level} ${name}:`);
      },
    });
     
    log.trace('trace');
    log.debug('debug');
    log.getLogger('critical').info('Something significant happened');
    log.log('log');
    log.info('info');
    log.warn('warn');
    log.error('error');

    Output

    output

    Custom options

    const log = require('loglevel');
    const prefix = require('loglevel-plugin-prefix');
     
    prefix.reg(log);
    log.enableAll();
     
    prefix.apply(log, {
      template: '[%t] %l (%n) static text:',
      levelFormatter(level) {
        return level.toUpperCase();
      },
      nameFormatter(name) {
        return name || 'global';
      },
      timestampFormatter(date) {
        return date.toISOString();
      },
    });
     
    log.info('%s prefix', 'template');
     
    const fn = (level, name, timestamp) => `[${timestamp}${level} (${name}) static text:`;
     
    prefix.apply(log, { format: fn });
     
    log.info('%s prefix', 'functional');
     
    prefix.apply(log, { template: '[%t] %l (%n) static text:' });
     
    log.info('again %s prefix', 'template');

    Output

    [2017-05-29T12:53:46.000Z] INFO (global) static text: template prefix
    [2017-05-29T12:53:46.000Z] INFO (global) static text: functional prefix
    [2017-05-29T12:53:46.000Z] INFO (global) static text: again template prefix
    

    Option inheritance

    const log = require('loglevel');
    const prefix = require('loglevel-plugin-prefix');
     
    prefix.reg(log);
    log.enableAll();
     
    log.info('root');
     
    const chicken = log.getLogger('chicken');
    chicken.info('chicken');
     
    prefix.apply(chicken, { template: '%l (%n):' });
    chicken.info('chicken');
     
    prefix.apply(log);
    log.info('root');
     
    const egg = log.getLogger('egg');
    egg.info('egg');
     
    const fn = (level, name) => `${level} (${name}):`;
     
    prefix.apply(egg, { format: fn });
    egg.info('egg');
     
    prefix.apply(egg, {
      levelFormatter(level) {
        return level.toLowerCase();
      },
    });
    egg.info('egg');
     
    chicken.info('chicken');
    log.info('root');

    Output

    root
    chicken
    INFO (chicken): chicken
    [16:53:46] INFO: root
    [16:53:46] INFO: egg
    INFO (egg): egg
    info (egg): egg
    INFO (chicken): chicken
    [16:53:46] INFO: root
    

    Install

    npm i loglevel-plugin-prefix

    DownloadsWeekly Downloads

    609,069

    Version

    0.8.4

    License

    MIT

    Unpacked Size

    63.2 kB

    Total Files

    15

    Last publish

    Collaborators

    • kutuluk