trying to expand a simple polygon

[Bradford Vesely]

Dear Group:

I am trying to expand a simple polygon.  The problem is that I keep getting a corner that does not match the original polygon.  Is there a way to change this.

var geometryFactory = new jsts.geom.GeometryFactory();

var shell = geometryFactory.createPolygon(geoInput); 

var polygon = shell.buffer(spacing,0)  //zero should set to no specialized corner but does not work.

Thank you for your help,

Brad

[Bradford Vesely]

FYI, here is the example that I am following 

https://stackoverflow.com/questions/11942046/scale-a-polygon-so-the-edges-match-up