Grouping points after cut plane three js with new library - three.js

Question

Regarding the discussion in this link, where the object is a THREE.Geometry(), anyone has any idea to implement this code:
function getContours(points, contours, firstRun) {
//console.log("firstRun:", firstRun);
let contour = [];
// find first line for the contour
let firstPointIndex = 0;
let secondPointIndex = 0;
let firstPoint, secondPoint;
for (let i = 0; i < points.length; i++) {
if (points[i].checked == true) continue;
firstPointIndex = i;
firstPoint = points[firstPointIndex];
firstPoint.checked = true;
secondPointIndex = getPairIndex(firstPoint, firstPointIndex, points);
secondPoint = points[secondPointIndex];
secondPoint.checked = true;
contour.push(firstPoint.clone());
contour.push(secondPoint.clone());
break;
}
contour = getContour(secondPoint, points, contour);
contours.push(contour);
let allChecked = 0;
points.forEach(p => { allChecked += p.checked == true ? 1 : 0; });
console.log("allChecked: ", allChecked == points.length);
if (allChecked != points.length) { return getContours(points, contours, false); }
return contours;
}
function getContour(currentPoint, points, contour){
let p1Index = getNearestPointIndex(currentPoint, points);
let p1 = points[p1Index];
p1.checked = true;
let p2Index = getPairIndex(p1, p1Index, points);
let p2 = points[p2Index];
p2.checked = true;
let isClosed = p2.equals(contour[0], tolerance);
if (!isClosed) {
contour.push(p2.clone());
return getContour(p2, points, contour);
} else {
contour.push(contour[0].clone());
return contour;
}
}
function getNearestPointIndex(point, points){
let index = 0;
for (let i = 0; i < points.length; i++){
let p = points[i];
if (p.checked == false && p.equals(point, tolerance)){
index = i;
break;
}
}
return index;
}
function getPairIndex(point, pointIndex, points) {
let index = 0;
for (let i = 0; i < points.length; i++) {
let p = points[i];
if (i != pointIndex && p.checked == false && p.faceIndex == point.faceIndex) {
index = i;
break;
}
}
return index;
}
With new three library the object is a THREE.BufferGeometry() that has no face(s) and no checked.
I need to connect the points between themselves (separate arrays) where the plane passes.