javascript function to get a OBJ file format string from a three.js BufferGeometry object

objStringFromBufferGeometry: function (geom) {
    var s = '';
    var geometry = new THREE.Geometry().fromBufferGeometry( geom );
    for (var i = 0; i < geometry.vertices.length; i++) {
      var vertex = geometry.vertices[i];
      s += 'v '+ vertex.x + ' ' + vertex.y + ' '+ vertex.z + '\n';
    }

    for (var i = 0; i < geometry.faces.length; i++) {
      s += 'f '+ (geometry.faces[i].a+1) + ' ' + (geometry.faces[i].b+1) + ' ' + (geometry.faces[i].c+1);

      if (geometry.faces[i].d !== undefined) {
        s += ' '+ (geometry.faces[i].d+1);
      }
      s+= '\n';
    }

    return s;
  }