ss-logger

A super simple JavaScript logger. It allows labels/tags, custom logging levels, custom output formatting and it's small. It has no dependancies.

Examples

// Standard usage
const log = require('ss-logger')();

log.info('My first info line.');
log.warn({my_obj: 'a'});
log.error('My first error line.');

// Output:
// stdout: 2017-03-10T09:44:06.391Z info: My first info line.
// stderr: 2017-03-10T09:44:06.396Z warn: {"my_obj":"a"}
// stderr: 2017-03-10T09:44:06.394Z error: My first error line.

Meta

• license: Apache-2.0

createLogger

The ss-logger module returns createLogger() by default.

Parameters

• label string? The label to print out on lines. Recommend not to use spaces.

Examples

// Each log line can have it's own label / tag.

const myFuncLog = require('ss-logger')('MyFunc');
const yourMethodLog = require('ss-logger')('Yours');

myFuncLog.info('My first info line.');
yourMethodLog.warn({obj: 'a'});
yourMethodLog.error('My first error line.');

// Output:
// stdout: 2017-03-10T09:44:06.391Z info MyFunc: My first info.
// stderr: 2017-03-10T09:44:06.396Z warn Yours: {"obj":"a"}
// stderr: 2017-03-10T09:44:06.394Z error Yours: My first err.

setOutput

By default the error and warn levels log output to console.error, while all other levels log output to console.log.

Parameters

• output Object An object with 'log' and 'error' functions.

Examples

log.setOutput({
    error: myErrorStream
    log: myLogStream
});

• Throws Error

setFormatFunction

Override the default format function. Must supply a function to handle the following parameters (date, level, fnLabel, ...msgArgs).

Parameters

• newFormatFunction Function The new function to do the formatting of the output.

Examples

log.setFormatFunction(function (date, level, label, ...msgArgs) {
      const l = level.toUpperCase();
      const d = date.getTime();
      const s = msgArgs.toString();
      return `${l} ${d} ${s}`;
});
log.info('Another info line.');

// Output:
// stdout: INFO 1489198884388 Another info line.

• Throws Error

setLevel

Set the log level of the logger. Anything equal to or below this level will be output. The default level is info. The available log levels are:

• error
• warn
• info
• verbose
• debug
• silly

Parameters

• newLogLevel number The new level.

Examples

log.setLevel(log.levels.error);

log.debug('This happened!');
log.info('My first info line.');
log.warn('You have an object: ', {obj: 'a'});
log.error('My second error line.');

// Output:
// stderr: 2017-03-10T09:44:06.394Z error: My second error line.

• Throws Error

Set debug log level from console

From the terminal:

DEBUG=MyFunction node app.js

Note: you can also use the following to enable debugging for all output: DEBUG=* node app.js

// app.js

const myFuncLog = require('ss-logger')('MyFunc');
const yourMethodLog = require('ss-logger')('Yours');

myFuncLog.debug('My debug message.');
yourMethodLog.debug('Your debug message');

// Output:
// stdout: 2017-03-10T09:44:06.391Z info MyFunc: My debug message.