const log4js = require('../lib/log4js'); log4js.addLayout( 'json', (config) => function (logEvent) { return JSON.stringify(logEvent) + config.separator; } ); log4js.configure({ appenders: { out: { type: 'stdout', layout: { type: 'json', separator: ',' } }, }, categories: { default: { appenders: ['out'], level: 'info' }, }, }); const logger = log4js.getLogger('json-test'); logger.info('this is just a test'); logger.error('of a custom appender'); logger.warn('that outputs json'); log4js.shutdown(() => {});