Buffer clip using ESRI JS Geometry Engine

Today I have almost finished coding a mapping application using ArcGIS JS 3.17. You can try it (http://maps.cga.harvard.edu/housing/). Very interesting it was the use of the ESRI geometry engine (https://developers.arcgis.com/javascript/3/jsapi/esri.geometry.geometryengine-amd.html). Below it a screen shot of a buffer (black area) clipped by a polygon (red line).https://gzambotti.github.io/housing/