Migrate @turf/line-offset to TypeScript

packages/turf-line-offset/index.js → packages/turf-line-offset/index.ts

@@ -5,8 +5,10 @@ import {
   lineString,
   multiLineString,
   lengthToDegrees,
+  Units,
 } from "@turf/helpers";
 import { intersection } from "./lib/intersection.js";
+import { Feature, LineString, MultiLineString, Position } from "geojson";
 
 /**
  * Takes a {@link LineString|line} and returns a {@link LineString|line} at offset by the specified distance.
@@ -26,25 +28,29 @@ import { intersection } from "./lib/intersection.js";
  * var addToMap = [offsetLine, line]
  * offsetLine.properties.stroke = "#00F"
  */
-function lineOffset(geojson, distance, options) {
+function lineOffset<T extends LineString | MultiLineString>(
+  geojson: Feature<T> | T,
+  distance: number,
+  options: { units?: Units } = {}
+) {
   // Optional parameters
   options = options || {};
   if (!isObject(options)) throw new Error("options is invalid");
-  var units = options.units;
+  const { units = "kilometers" } = options;
 
   // Valdiation
   if (!geojson) throw new Error("geojson is required");
   if (distance === undefined || distance === null || isNaN(distance))
     throw new Error("distance is required");
 
   var type = getType(geojson);
-  var properties = geojson.properties;
+  var properties = geojson.type === "Feature" ? geojson.properties : {};
 
   switch (type) {
     case "LineString":
       return lineOffsetFeature(geojson, distance, units);
     case "MultiLineString":
-      var coords = [];
+      var coords: Position[][] = [];
       flattenEach(geojson, function (feature) {
         coords.push(
           lineOffsetFeature(feature, distance, units).geometry.coordinates
@@ -65,11 +71,15 @@ function lineOffset(geojson, distance, options) {
  * @param {string} [units=kilometers] units
  * @returns {Feature<LineString>} Line offset from the input line
  */
-function lineOffsetFeature(line, distance, units) {
-  var segments = [];
+function lineOffsetFeature(
+  line: Feature<LineString | MultiLineString> | LineString | MultiLineString,
+  distance: number,
+  units: Units
+) {
+  var segments: [[number, number], [number, number]][] = [];
   var offsetDegrees = lengthToDegrees(distance, units);
   var coords = getCoords(line);
-  var finalCoords = [];
+  var finalCoords: [number, number][] = [];
   coords.forEach(function (currentCoords, index) {
     if (index !== coords.length - 1) {
       var segment = processSegment(
@@ -101,7 +111,10 @@ function lineOffsetFeature(line, distance, units) {
       }
     }
   });
-  return lineString(finalCoords, line.properties);
+  return lineString(
+    finalCoords,
+    line.type === "Feature" ? line.properties : {}
+  );
 }
 
 /**
@@ -114,7 +127,11 @@ function lineOffsetFeature(line, distance, units) {
  * @param {number} offset Offset
  * @returns {Array<Array<number>>} offset points
  */
-function processSegment(point1, point2, offset) {
+function processSegment(
+  point1: [number, number],
+  point2: [number, number],
+  offset: number
+): [[number, number], [number, number]] {
   var L = Math.sqrt(
     (point1[0] - point2[0]) * (point1[0] - point2[0]) +
       (point1[1] - point2[1]) * (point1[1] - point2[1])

packages/turf-line-offset/lib/intersection.js → packages/turf-line-offset/lib/intersection.ts

@@ -11,7 +11,7 @@
  * @param {Array<Array<number>>} segment - 2 vertex line segment
  * @returns {Array<number>} coordinates [x, y]
  */
-function ab(segment) {
+function ab(segment: [number, number][]): [number, number] {
   var start = segment[0];
   var end = segment[1];
   return [end[0] - start[0], end[1] - start[1]];
@@ -25,7 +25,7 @@ function ab(segment) {
  * @param {Array<number>} v2 coordinates [x, y]
  * @returns {Array<number>} Cross Product
  */
-function crossProduct(v1, v2) {
+function crossProduct(v1: [number, number], v2: [number, number]) {
   return v1[0] * v2[1] - v2[0] * v1[1];
 }
 
@@ -37,7 +37,7 @@ function crossProduct(v1, v2) {
  * @param {Array<number>} v2 coordinates [x, y]
  * @returns {Array<number>} Add
  */
-function add(v1, v2) {
+function add(v1: [number, number], v2: [number, number]): [number, number] {
   return [v1[0] + v2[0], v1[1] + v2[1]];
 }
 
@@ -49,7 +49,7 @@ function add(v1, v2) {
  * @param {Array<number>} v2 coordinates [x, y]
  * @returns {Array<number>} Sub
  */
-function sub(v1, v2) {
+function sub(v1: [number, number], v2: [number, number]): [number, number] {
   return [v1[0] - v2[0], v1[1] - v2[1]];
 }
 
@@ -61,7 +61,7 @@ function sub(v1, v2) {
  * @param {Array<number>} v coordinates [x, y]
  * @returns {Array<number>} scalarMult
  */
-function scalarMult(s, v) {
+function scalarMult(s: number, v: [number, number]): [number, number] {
   return [s * v[0], s * v[1]];
 }
 
@@ -73,7 +73,10 @@ function scalarMult(s, v) {
  * @param {Array<number>} b coordinates [x, y]
  * @returns {Array<number>} intersection
  */
-function intersectSegments(a, b) {
+function intersectSegments(
+  a: [number, number][],
+  b: [number, number][]
+): [number, number] {
   var p = a[0];
   var r = ab(a);
   var q = b[0];
@@ -95,7 +98,7 @@ function intersectSegments(a, b) {
  * @param {Array<number>} b coordinates [x, y]
  * @returns {boolean} true if a and b are parallel (or co-linear)
  */
-function isParallel(a, b) {
+function isParallel(a: [number, number][], b: [number, number][]): boolean {
   var r = ab(a);
   var s = ab(b);
   return crossProduct(r, s) === 0;
@@ -109,10 +112,10 @@ function isParallel(a, b) {
  * @param {Array<number>} b coordinates [x, y]
  * @returns {Array<number>|boolean} true if a and b are parallel (or co-linear)
  */
-function intersection(a, b) {
+export function intersection(
+  a: [number, number][],
+  b: [number, number][]
+): [number, number] | false {
   if (isParallel(a, b)) return false;
   return intersectSegments(a, b);
 }
-
-export { intersection };
-export default intersection;

packages/turf-line-offset/package.json

@@ -65,12 +65,14 @@
     "tape": "^5.9.0",
     "tsup": "^8.4.0",
     "tsx": "^4.19.4",
+    "typescript": "^5.8.3",
     "write-json-file": "^6.0.0"
   },
   "dependencies": {
     "@turf/helpers": "workspace:*",
     "@turf/invariant": "workspace:*",
     "@turf/meta": "workspace:*",
-    "@types/geojson": "^7946.0.10"
+    "@types/geojson": "^7946.0.10",
+    "tslib": "^2.8.1"
   }
 }

packages/turf-line-offset/test.ts

@@ -27,15 +27,15 @@ let fixtures = fs.readdirSync(directories.in).map((filename) => {
 test("turf-line-offset", (t) => {
   fixtures.forEach((fixture) => {
     const name = fixture.name;
-    const geojson = fixture.geojson;
+    const geojson = fixture.geojson as any;
     const properties = geojson.properties || {};
     const distance = properties.distance || 50;
     const units = properties.units;
 
     const output = truncate(lineOffset(geojson, distance, { units: units }), {
       precision: 4,
     });
-    output.properties.stroke = "#00F";
+    output.properties!.stroke = "#00F";
     const results = featureCollection([output, geojson]);
 
     if (process.env.REGEN)
@@ -54,8 +54,8 @@ test("turf-line-offset - Throws Errors", (t) => {
     [10, 10],
     [0, 0],
   ]);
-  t.throws(() => lineOffset(), /geojson is required/);
-  t.throws(() => lineOffset(line), /distance is required/);
+  t.throws(() => (lineOffset as any)(), /geojson is required/);
+  t.throws(() => (lineOffset as any)(line), /distance is required/);
   t.end();
 });