union: function union(a, b) {
let start = a.compareBoundaryPoints(a.START_TO_START, b) < 0 ? a : b;
let end = a.compareBoundaryPoints(a.END_TO_END, b) > 0 ? a : b;
union: function union(a, b) {
let start = a.compareBoundaryPoints(a.START_TO_START, b) < 0 ? a : b;
let end = a.compareBoundaryPoints(a.END_TO_END, b) > 0 ? a : b;