code: function formatConfig(config) {
    const result = {
      appenders: {
        out: { type: 'console' }
      },
      categories: {
        default: {
          appenders: ['out'],
          level: 'info'
        }
      }
    }
    for (const appender of config.appenders) {
      result.appenders[appender.type] = Object.assign({}, appender)
      ;(result.categories[appender.category] ||
        (result.categories[appender.category] = {
          appenders: [],
          level: 'info'
        }))['appenders'].push(appender.type)
    }
    return result
  }
docs: format log4jsConfig passed by return v2.x styled config caused by Migrating from log4js versions older than 2.x