added shift

Author: DanielJDufour

README.md

@@ -25,6 +25,7 @@ Bounding boxes, or rectangular extents, are represented as an array of 4 numbers
 - [polygon](#polygon)
 - [reproject](#reproject)
 - [scale](#scale)
+- [shift](#shift)
 - [split](#split)
 - [union](#union)
 - [validate](#validate)
@@ -270,6 +271,22 @@ scale([0, 9, 50, 200], [2, 10]);
 [0, 90, 100, 2000]
 ```
 
+### shift
+Shift bounding box horizontally and/or vertically
+```js
+// shift bounding box overlapping left "edge"
+// to the right, so it overlaps the right "edge"
+shift([-200, 40, -160, 90], { x: 360 })
+[160,40,200,90];
+
+// shift horizontally and vertically
+shift([-185, 90, -180, 95], [360, -90])
+[175, 0, 180, 5]
+
+// same as above
+shift([-185, 90, -180, 95], { x: 360, y: -90 });
+```
+
 ### split
 Split bounding box that crosses given x or y boundaries.  For example, split a bbox that crosses the antimeridian into two bounding boxes.
 ```js

index.js

@@ -20,6 +20,7 @@ const preciseDivide = require("./precise/divide.js");
 const preciseReproject = require("./precise/reproject.js");
 const reproject = require("./reproject.js");
 const scale = require("./scale.js");
+const shift = require("./shift.js");
 const split = require("./split.js");
 const validate = require("./validate.js");
 const preciseValidate = require("./precise/validate.js");
@@ -46,6 +47,7 @@ const bboxfns = {
   preciseReproject,
   reproject,
   scale,
+  shift,
   split,
   validate,
   preciseValidate,

package.json

@@ -28,6 +28,7 @@
     "precise/divide.js",
     "precise/reproject.js",
     "precise/validate.js",
+    "shift.js",
     "split.js",
     "union.js",
     "validate.js"

shift.js

@@ -0,0 +1,19 @@
+function shift([xmin, ymin, xmax, ymax], dist) {
+  const x =
+    Array.isArray(dist) && dist.length >= 1
+      ? dist[0]
+      : typeof dist.x === "number"
+      ? dist.x
+      : 0;
+  const y =
+    Array.isArray(dist) && dist.length >= 2
+      ? dist[1]
+      : typeof dist.y === "number"
+      ? dist.y
+      : 0;
+
+  return [xmin + x, ymin + y, xmax + x, ymax + y];
+}
+
+module.exports = shift;
+module.exports.default = shift;

test.js

@@ -44,6 +44,7 @@ const {
   reproject,
   preciseReproject,
   scale,
+  shift,
   split,
   preciseDivide,
   validate,
@@ -80,10 +81,10 @@ test("bboxArray", ({ eq }) => {
 });
 
 test("bboxSize", ({ eq }) => {
-  eq(
-    bboxSize([-180, 84.48577680525165, -179, 86.06126914660831]),
-    [1, 1.5754923413566644]
-  );
+  eq(bboxSize([-180, 84.48577680525165, -179, 86.06126914660831]), [
+    1,
+    1.5754923413566644
+  ]);
   eq(bboxSize([-540, -90, -180, 90]), [360, 180]);
 });
 
@@ -629,6 +630,16 @@ test("scale", async ({ eq }) => {
   eq(scale([0, 9, 50, 200], [2, 10]), [0, 90, 100, 2000]);
 });
 
+test("shift", async ({ eq }) => {
+  eq(shift([-200, 40, -160, 90], { x: 360 }), [160, 40, 200, 90]);
+  eq(shift([-185, 40, -180, 90], { x: 360 }), [175, 40, 180, 90]);
+  eq(shift([-185, 40, -180, 90], [360, 0]), [175, 40, 180, 90]);
+  eq(shift([-185, 90, -180, 95], [360, -90]), [175, 0, 180, 5]);
+  eq(shift([-185, 90, -180, 95], { x: 360, y: -90 }), [175, 0, 180, 5]);
+  eq(shift([-185, 90, -180, 95], {}), [-185, 90, -180, 95]);
+  eq(shift([-185, 90, -180, 95], []), [-185, 90, -180, 95]);
+});
+
 test("split", async ({ eq }) => {
   eq(split([-180, -90, 180, 90], { x: [-180, 180], y: [-90, 90] }), [
     [-180, -90, 180, 90]