feat: copied from github.com/seddonm1/quickjs

track_points.js

@@ -0,0 +1,39 @@
+// simple approximate distance function returning distance between two points in meters
+function distance(lat0, lon0, lat1, lon1) {
+    if ((lat0 == lat1) && (lon0 == lon1)) {
+        return 0;
+    } else {
+        const radlat0 = Math.PI * lat0 / 180;
+        const radlat1 = Math.PI * lat1 / 180;
+        const theta = lon0 - lon1;
+        const radtheta = Math.PI * theta / 180;
+        let dist = Math.sin(radlat0) * Math.sin(radlat1) + Math.cos(radlat0) * Math.cos(radlat1) * Math.cos(radtheta);
+        if (dist > 1) {
+            dist = 1;
+        }
+        dist = Math.acos(dist);
+        dist = dist * 180 / Math.PI;
+        return dist * 60 * 1853.159;
+    }
+}
+
+// calculate the total length of a set of input features in canadian football fields
+function calculate(data) {
+    // canadian football fields are 140 meters
+    const candadian_football_field = 140;
+
+    return data.features.reduce(
+        (accumulator, currentValue, currentIndex, array) => {
+            if (currentIndex == 0) {
+                return 0
+            } else {
+                const previousValue = array[currentIndex - 1];
+                const dist = distance(currentValue.geometry.coordinates[1], currentValue.geometry.coordinates[0], previousValue.geometry.coordinates[1], previousValue.geometry.coordinates[0]);
+                return accumulator + dist / candadian_football_field
+            }
+        },
+        0
+    )
+}
+
+calculate(data)