filter duplicates before checking point count, remove unnecessary slice

README.md

@@ -69,6 +69,8 @@ If you want to get involved with Hull.js development, just use <a href="https://
 
 ## Changelog
 
+### 0.2.11 — 05.05.2019
+Return the first point as the last point when fewer than 4 unique points are provided.
 ### 0.2.10 — 04.09.2016
 Fixed missing "var" declaration
 ### 0.2.9 — 28.07.2016

dist/hull.js

@@ -316,12 +316,12 @@ function hull(pointset, concavity, format) {
         points,
         maxEdgeLen = concavity || 20;
 
-    if (pointset.length < 4) {
-        return pointset.concat([pointset[0]]).slice();
-    }
-
     points = _filterDuplicates(_sortByX(formatUtil.toXy(pointset, format)));
 
+    if (points.length < 4) {
+        return points.concat([points[0]]);
+    }
+
     occupiedArea = _occupiedArea(points);
     maxSearchArea = [
         occupiedArea[0] * MAX_SEARCH_BBOX_SIZE_PERCENT,

src/hull.js

@@ -171,12 +171,12 @@ function hull(pointset, concavity, format) {
         points,
         maxEdgeLen = concavity || 20;
 
-    if (pointset.length < 4) {
-        return pointset.concat([pointset[0]]).slice();
-    }
-
     points = _filterDuplicates(_sortByX(formatUtil.toXy(pointset, format)));
 
+    if (points.length < 4) {
+        return points.concat([points[0]]);
+    }
+
     occupiedArea = _occupiedArea(points);
     maxSearchArea = [
         occupiedArea[0] * MAX_SEARCH_BBOX_SIZE_PERCENT,

test/hull.js

@@ -20,9 +20,21 @@ module.exports = function() {
         assert.deepEqual(hull(points, 0.0011, ['.lng', '.lat']), expected);
     });
 
-    it('should return first point as last point', function() {
+    it('should append the first point', function() {
         var points = [[141, 408], [160, 400], [177, 430]];
         var expected = [[141, 408], [160, 400], [177, 430], [141, 408]];
         assert.deepEqual(hull(points, 50), expected);
     });
+
+    it('should not append the first point', function() {
+        var points = [[141, 408], [160, 400], [141, 408]];
+        var expected = [[141, 408], [160, 400], [141, 408]];
+        assert.deepEqual(hull(points, 50), expected);
+    });
+
+    it('should not append the first point', function() {
+        var points = [[141, 408], [160, 400], [177, 430], [141, 408]];
+        var expected = [[141, 408], [160, 400], [177, 430], [141, 408]];
+        assert.deepEqual(hull(points, 50), expected);
+    });
 }