Provides a slim and easy to use json-layout for log4js-node

Usage no npm install needed!

<script type="module">
  import log4jsJsonLayout from 'https://cdn.skypack.dev/log4js-json-layout';



A slim and easy to use JSON layout for log4js-node.


Build Status


npm install log4js-json-layout --save

Example Output


{"startTime":"2017-07-27T00:01:05.175Z","categoryName":"/path/to/file/redis-client.js","level":"DEBUG","data":"Connection to Redis successful!"}


Set the layout type to json.

Each log object contains the following properties:

  • startTime - time in ISO 8601 format
  • categoryName - specified when log4js is initialized
  • data - if the log message is a string, otherwise omitted
  • level - level in human readable format
  • source - if provided, will be included

Additional properties can be specified as extra arguments of object type during invocation of log function. Static or constant properties can be specified using the static config option.


  • type - string, always json
  • source - optional string, just sets the property source. Example value: development
  • include - array of properties to include in the log object
  • colors - boolean; off by default. If set to true, colorizes the output using log4js default color scheme based on log level. Useful for development, do not use for storing logs
  • static - object, name value pairs of this object are added to output
  • dynamic - object, where each value is a no-argument function that must return a string/number/boolean. The key and the function's return value are added to the output

Example Config

const log4js = require('log4js');
const jsonLayout = require('log4js-json-layout');

log4js.addLayout('json', jsonLayout);


appenders = [{
  type: 'console',
  layout: {
    type: 'json',

More options:

appenders = [{
  type: 'console',
  messageParam: 'msg',
  layout: {
    type: 'json',
    source: 'development',
    static: {
      appName: 'mysuperbapp'
    dynamic: {
      transactionId: function() {
        return 'tx-id'; // string
      isAdmin: function() {
        return 1>0; // boolean
      countLogin: function() {
        return 20; // number
    include: ['startTime', 'categoryName'],

const logger = log4js.getLogger('info');

logger.info('Test log');


{"startTime":"2017-07-27T00:01:05.175Z","categoryName":"/path/to/file/redis-client.js","level":"DEBUG","transactionId": "tx-id","isAdmin": true,"countLogin": 20,"data":"Test log",}