code: function formatConfig(config) {
    var result = {
      appenders: {
        out: { type: 'console' }
      },
      categories: {
        default: {
          appenders: ['out'],
          level: 'info'
        }
      }
    };
    var _iteratorNormalCompletion = true;
    var _didIteratorError = false;
    var _iteratorError = undefined;
  
    try {
      for (var _iterator = config.appenders[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
        var appender = _step.value;
  
        result.appenders[appender.type] = Object.assign({}, appender);(result.categories[appender.category] || (result.categories[appender.category] = {
          appenders: [],
          level: 'info'
        }))['appenders'].push(appender.type);
      }
    } catch (err) {
      _didIteratorError = true;
      _iteratorError = err;
    } finally {
      try {
        if (!_iteratorNormalCompletion && _iterator.return) {
          _iterator.return();
        }
      } finally {
        if (_didIteratorError) {
          throw _iteratorError;
        }
      }
    }
  
    return result;
  }
docs: format log4jsConfig passed by return v2.x styled config caused by Migrating from log4js versions older than 2.x