Add array/slidingWindow method (#36)

* Add sliding window method

* Add additional test cases

* Update after code review

* Update description for method and test cases

* Update test cases descriptions

Co-authored-by: krystianborucinski <krystian.borucinski@sandstream.pl>

Author: 2 people

README.md

@@ -479,6 +479,34 @@ Skips the given count of elements from the given array.
 ```
 <!-- prettier-ignore-end -->
 
+#### slidingWindow
+
+Returns a new array composed of tuples of the given sliding window length of consecutive elements.
+
+##### Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(count: number) => (xs: any[]) => any[][]
+```
+<!-- prettier-ignore-end -->
+
+##### Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+slidingWindow(2)([1, 2, 3, 4]); // ⇒ [[1, 2], [2, 3], [3, 4]]
+```
+
+```javascript
+slidingWindow(3)([1, 2, 3, 4, 5]); // ⇒ [[1, 2, 3], [2, 3, 4], [3, 4, 5]]
+```
+
+```javascript
+slidingWindow(1)([1, 2, 3, 4, 5, 6]); // ⇒ [[1], [2], [3], [4], [5], [6]]
+```
+<!-- prettier-ignore-end -->
+
 #### sort
 
 Sorts the given array without mutating it.

array/README.md

@@ -462,6 +462,34 @@ Skips the given count of elements from the given array.
 ```
 <!-- prettier-ignore-end -->
 
+# slidingWindow
+
+Returns a new array composed of tuples of the given sliding window length of consecutive elements.
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(count: number) => (xs: any[]) => any[][]
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+slidingWindow(2)([1, 2, 3, 4]); // ⇒ [[1, 2], [2, 3], [3, 4]]
+```
+
+```javascript
+slidingWindow(3)([1, 2, 3, 4, 5]); // ⇒ [[1, 2, 3], [2, 3, 4], [3, 4, 5]]
+```
+
+```javascript
+slidingWindow(1)([1, 2, 3, 4, 5, 6]); // ⇒ [[1], [2], [3], [4], [5], [6]]
+```
+<!-- prettier-ignore-end -->
+
 # sort
 
 Sorts the given array without mutating it.

array/index.js

@@ -33,6 +33,7 @@ import shuffle from "./shuffle.js";
 import shuffleInPlace from "./shuffleInPlace.js";
 import single from "./single.js";
 import skip from "./skip.js";
+import slidingWindow from "./slidingWindow.js";
 import sort from "./sort.js";
 import sum from "./sum.js";
 import take from "./take.js";
@@ -76,6 +77,7 @@ export {
   shuffleInPlace,
   single,
   skip,
+  slidingWindow,
   sort,
   sum,
   take,
@@ -120,6 +122,7 @@ export default {
   shuffleInPlace,
   single,
   skip,
+  slidingWindow,
   sort,
   sum,
   take,

array/index.ts

@@ -33,6 +33,7 @@ import shuffle from "./shuffle";
 import shuffleInPlace from "./shuffleInPlace";
 import single from "./single";
 import skip from "./skip";
+import slidingWindow from "./slidingWindow";
 import sort from "./sort";
 import sum from "./sum";
 import take from "./take";
@@ -76,6 +77,7 @@ export {
   shuffleInPlace,
   single,
   skip,
+  slidingWindow,
   sort,
   sum,
   take,
@@ -120,6 +122,7 @@ export default {
   shuffleInPlace,
   single,
   skip,
+  slidingWindow,
   sort,
   sum,
   take,

array/slidingWindow.js

@@ -0,0 +1,4 @@
+export default count => xs =>
+  xs
+    .map((_, index, source) => source.slice(index, index + count))
+    .filter(element => element.length > 0 && element.length === count);

array/slidingWindow.json

@@ -0,0 +1,20 @@
+{
+  "name": "slidingWindow",
+  "description": "Returns a new array composed of tuples of the given sliding window length of consecutive elements.",
+  "signature": "(count: number) => (xs: any[]) => any[][]",
+  "examples": [
+    {
+      "language": "javascript",
+      "content": "slidingWindow(2)([1, 2, 3, 4]); // ⇒ [[1, 2], [2, 3], [3, 4]]"
+    },
+    {
+      "language": "javascript",
+      "content": "slidingWindow(3)([1, 2, 3, 4, 5]); // ⇒ [[1, 2, 3], [2, 3, 4], [3, 4, 5]]"
+    },
+    {
+      "language": "javascript",
+      "content": "slidingWindow(1)([1, 2, 3, 4, 5, 6]); // ⇒ [[1], [2], [3], [4], [5], [6]]"
+    }
+  ],
+  "questions": ["TODO: List questions that may this function answer."]
+}

array/slidingWindow.md

@@ -0,0 +1,27 @@
+# slidingWindow
+
+Returns a new array composed of tuples of the given sliding window length of consecutive elements.
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(count: number) => (xs: any[]) => any[][]
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+slidingWindow(2)([1, 2, 3, 4]); // ⇒ [[1, 2], [2, 3], [3, 4]]
+```
+
+```javascript
+slidingWindow(3)([1, 2, 3, 4, 5]); // ⇒ [[1, 2, 3], [2, 3, 4], [3, 4, 5]]
+```
+
+```javascript
+slidingWindow(1)([1, 2, 3, 4, 5, 6]); // ⇒ [[1], [2], [3], [4], [5], [6]]
+```
+<!-- prettier-ignore-end -->

array/slidingWindow.test.ts

@@ -0,0 +1,56 @@
+/* eslint-env jest */
+// @ts-ignore ambiguous import
+import slidingWindow from "./slidingWindow.ts";
+
+describe("slidingWindow", () => {
+  it("should return an array of pairs of consecutive elements for sliding window length of 2", () => {
+    expect(slidingWindow(2)([1, 2, 3, 4, 5, 6])).toEqual([
+      [1, 2],
+      [2, 3],
+      [3, 4],
+      [4, 5],
+      [5, 6]
+    ]);
+  });
+
+  it("should return an array composed of triples of consecutive elements for sliding window length of 3", () => {
+    expect(slidingWindow(3)([1, 2, 3, 4, 5, 6])).toEqual([
+      [1, 2, 3],
+      [2, 3, 4],
+      [3, 4, 5],
+      [4, 5, 6]
+    ]);
+  });
+
+  it("should return an array composed of quadruples of consecutive elements for sliding window length of 4", () => {
+    expect(slidingWindow(4)([1, 2, 3, 4, 5, 6])).toEqual([
+      [1, 2, 3, 4],
+      [2, 3, 4, 5],
+      [3, 4, 5, 6]
+    ]);
+  });
+
+  it("should return a wrapped array when sliding window size is equal to length of the given array", () => {
+    expect(slidingWindow(6)([1, 2, 3, 4, 5, 6])).toEqual([[1, 2, 3, 4, 5, 6]]);
+  });
+
+  it("should return an array of wrapped values in arrays when sliding window length is 1", () => {
+    expect(slidingWindow(1)([1, 2, 3, 4, 5, 6])).toEqual([
+      [1],
+      [2],
+      [3],
+      [4],
+      [5],
+      [6]
+    ]);
+  });
+
+  it("should return an empty array when sliding window size is greater than length of the given array", () => {
+    expect(slidingWindow(3)([])).toEqual([]);
+  });
+
+  it("should return an empty array when sliding window size is less than or equal to zero", () => {
+    expect(slidingWindow(0)([1, 2, 3])).toEqual([]);
+    expect(slidingWindow(-1)([1, 2, 3])).toEqual([]);
+  });
+});

array/slidingWindow.ts

@@ -0,0 +1,4 @@
+export default (count: number) => (xs: any[]) =>
+  xs
+    .map((_, index, source) => source.slice(index, index + count))
+    .filter(element => element.length > 0 && element.length === count);