src/plugins/leaflet-draw/ext/Polygon.Intersect.js

/**
 * @class L.Polygon
 * @aka Polygon
 */
L.Polygon.include({

	// @method intersects(): boolean
	// Checks a polygon for any intersecting line segments. Ignores holes.
	intersects: function () {
		var polylineIntersects,
			points = this._getProjectedPoints(),
			len, firstPoint, lastPoint, maxIndex;

		if (this._tooFewPointsForIntersection()) {
			return false;
		}

		polylineIntersects = L.Polyline.prototype.intersects.call(this);

		// If already found an intersection don't need to check for any more.
		if (polylineIntersects) {
			return true;
		}

		len = points.length;
		firstPoint = points[0];
		lastPoint = points[len - 1];
		maxIndex = len - 2;

		// Check the line segment between last and first point. Don't need to check the first line segment (minIndex = 1)
		return this._lineSegmentsIntersectsRange(lastPoint, firstPoint, maxIndex, 1);
	}
});