How to use the d3-geo-projection.geoEckert4 function in d3-geo-projection

var _d3Geo = require("d3-geo");

var _projectionConfig = require("./projectionConfig");

var _projectionConfig2 = _interopRequireDefault(_projectionConfig);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

var projectionReference = {
  mercator: _d3Geo.geoMercator,
  miller: _d3GeoProjection.geoMiller,
  times: _d3GeoProjection.geoTimes,
  robinson: _d3GeoProjection.geoRobinson,
  winkel3: _d3GeoProjection.geoWinkel3,
  eckert4: _d3GeoProjection.geoEckert4,
  albersUsa: _d3Geo.geoAlbersUsa,
  orthographic: _d3Geo.geoOrthographic
};