JavaScript function to check if a point is in a polgyon

pointInPolygon.js

function pointInPolygon(point, vs) {
  // Taken from https://github.com/substack/point-in-polygon
  // Nice explainer at https://observablehq.com/@tmcw/understanding-point-in-polygon
  // ray-casting algorithm based on
  // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html

  let x = point[0], y = point[1];

  let inside = false;
  for (let i = 0, j = vs.length - 1; i < vs.length; j = i++) {
    let xi = vs[i][0], yi = vs[i][1];
    let xj = vs[j][0], yj = vs[j][1];

    let intersect = ((yi > y) != (yj > y))
    && (x < (xj - xi) * (y - yi) / (yj - yi) + xi);
    if (intersect) inside = !inside;
  }

  return inside;
};