JS verify coordinates inside polygon


JS verify coordinates inside polygon

Solution ES6

/**
 * Verify if point of coordinates (longitude, latitude) is polygon of coordinates
 * https://github.com/substack/point-in-polygon/blob/master/index.js
 * @param {number} latitude Latitude
 * @param {number} longitude Longitude
 * @param {array<[number,number]>} polygon Polygon contains arrays of points. One array have the following format: [latitude,longitude]
 */
export function isPointInPolygon(latitude, longitude, polygon) {
  if (typeof latitude !== "number" || typeof longitude !== "number") {
    throw new TypeError("Invalid latitude or longitude. Numbers are expected");
  } else if (!polygon || !Array.isArray(polygon)) {
    throw new TypeError("Invalid polygon. Array with locations expected");
  } else if (polygon.length === 0) {
    throw new TypeError("Invalid polygon. Non-empty Array expected");
  }

  const x = latitude;
  const y = longitude;

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

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

  return inside;
}

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