61 lines
1.9 KiB
JavaScript
Executable File
61 lines
1.9 KiB
JavaScript
Executable File
import { getCoords, getType } from '@turf/invariant';
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import { lineString } from '@turf/helpers';
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import nearestPointOnLine from '@turf/nearest-point-on-line';
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/**
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* Takes a {@link LineString|line}, a start {@link Point}, and a stop point
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* and returns a subsection of the line in-between those points.
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* The start & stop points don't need to fall exactly on the line.
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*
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* This can be useful for extracting only the part of a route between waypoints.
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*
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* @name lineSlice
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* @param {Coord} startPt starting point
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* @param {Coord} stopPt stopping point
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* @param {Feature<LineString>|LineString} line line to slice
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* @returns {Feature<LineString>} sliced line
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* @example
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* var line = turf.lineString([
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* [-77.031669, 38.878605],
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* [-77.029609, 38.881946],
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* [-77.020339, 38.884084],
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* [-77.025661, 38.885821],
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* [-77.021884, 38.889563],
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* [-77.019824, 38.892368]
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* ]);
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* var start = turf.point([-77.029609, 38.881946]);
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* var stop = turf.point([-77.021884, 38.889563]);
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*
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* var sliced = turf.lineSlice(start, stop, line);
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*
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* //addToMap
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* var addToMap = [start, stop, line]
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*/
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function lineSlice(startPt, stopPt, line) {
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// Validation
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var coords = getCoords(line);
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if (getType(line) !== "LineString")
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throw new Error("line must be a LineString");
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var startVertex = nearestPointOnLine(line, startPt);
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var stopVertex = nearestPointOnLine(line, stopPt);
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var ends;
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if (startVertex.properties.index <= stopVertex.properties.index) {
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ends = [startVertex, stopVertex];
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} else {
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ends = [stopVertex, startVertex];
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}
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var clipCoords = [ends[0].geometry.coordinates];
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for (
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var i = ends[0].properties.index + 1;
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i < ends[1].properties.index + 1;
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i++
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) {
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clipCoords.push(coords[i]);
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}
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clipCoords.push(ends[1].geometry.coordinates);
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return lineString(clipCoords, line.properties);
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}
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export default lineSlice;
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