ee.Feature.centroid

Returns a feature containing the point at the center of the highest-dimension components of the geometry of a feature. Lower-dimensional components are ignored, so the centroid of a geometry containing two polygons, three lines and a point is equivalent to the centroid of a geometry containing just the two polygons.
UsageReturns
Feature.centroid(maxError, proj)Feature
ArgumentTypeDetails
this: featureElementCalculates the centroid of this feature's default geometry.
maxErrorErrorMargin, default: nullThe maximum amount of error tolerated when performing any necessary reprojection.
projProjection, default: nullIf specified, the result will be in this projection. Otherwise it will be in WGS84.