How to use the jsts.geom function in jsts

const jsts_validate = function(geom) {
  if (geom instanceof jsts.geom.Polygon) {
    if (geom.isValid()) {
      geom.normalize() // validate does not pick up rings in the wrong order - this will fix that
      return geom // If the polygon is valid just return it
    }
    var polygonizer = new jsts.operation.polygonize.Polygonizer()
    jsts_addPolygon(geom, polygonizer)
    return jsts_toPolygonGeometry(polygonizer.getPolygons(), geom.getFactory())
  } else if (geom instanceof jsts.geom.MultiPolygon) {
    if (geom.isValid()) {
      geom.normalize() // validate does not pick up rings in the wrong order - this will fix that
      return geom // If the multipolygon is valid just return it
    }
    var polygonizer = new jsts.operation.polygonize.Polygonizer()

    for (var n = geom.getNumGeometries(); n > 0; n--) {
      jsts_addPolygon(geom.getGeometryN(n - 1), polygonizer)

var fs = require("fs"),
    util = require("util");
var async = require("async"),
    connect = require("connect"),
    pg = require("pg"),
    request = require("request"),
    jsts = require("jsts");

var factory = new jsts.geom.GeometryFactory();
var reader = new jsts.io.WKTReader(factory);

var zerocount = 0,
    nonzerocount = 0,
    undefcount = 0,
    existscount = 0;

var startPostgresClient = function(callback) {
  // postgres
  var client = new pg.Client({
    user: "",
    user: "openspaces",
    //user: "ggnpc",
    password: "",
    database: "openspaces",
    //database: "ggnpc",

// filter out unneccessary downloads
  var newOsmBoundarySources = {}
  Object.keys(zoneCfg).forEach((zoneName) => {
    zoneCfg[zoneName].forEach((op) => {
      if (op.source === 'overpass') {
        newOsmBoundarySources[op.id] = osmBoundarySources[op.id]
      }
    })
  })

  osmBoundarySources = newOsmBoundarySources
}

var geoJsonReader = new jsts.io.GeoJSONReader()
var geoJsonWriter = new jsts.io.GeoJSONWriter()
var precisionModel = new jsts.geom.PrecisionModel(1000000)
var precisionReducer = new jsts.precision.GeometryPrecisionReducer(precisionModel)
var distZones = {}
var minRequestGap = 4
var curRequestGap = 4

var safeMkdir = function (dirname, callback) {
  fs.mkdir(dirname, function (err) {
    if (err && err.code === 'EEXIST') {
      callback()
    } else {
      callback(err)
    }
  })
}

var debugGeo = function (op, a, b, reducePrecision) {

const jsts_validate = function(geom) {
  if (geom instanceof jsts.geom.Polygon) {
    if (geom.isValid()) {
      geom.normalize() // validate does not pick up rings in the wrong order - this will fix that
      return geom // If the polygon is valid just return it
    }
    var polygonizer = new jsts.operation.polygonize.Polygonizer()
    jsts_addPolygon(geom, polygonizer)
    return jsts_toPolygonGeometry(polygonizer.getPolygons(), geom.getFactory())
  } else if (geom instanceof jsts.geom.MultiPolygon) {
    if (geom.isValid()) {
      geom.normalize() // validate does not pick up rings in the wrong order - this will fix that
      return geom // If the multipolygon is valid just return it
    }
    var polygonizer = new jsts.operation.polygonize.Polygonizer()

    for (var n = geom.getNumGeometries(); n > 0; n--) {
      jsts_addPolygon(geom.getGeometryN(n - 1), polygonizer)
    }
    return jsts_toPolygonGeometry(polygonizer.getPolygons(), geom.getFactory())
  } else {
    return geom // In my case, I only care about polygon / multipolygon geometries
  }
}
const checkOverlap = (feature1, feature2) => {