Add array/zipN method (#38)

* Add zipN method

* Update after code review

* Update type

* Update after code review

* Add additional test case

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

Author: 2 people

README.md

@@ -569,6 +569,34 @@ Zips given arrays together into pairs.
 ```
 <!-- prettier-ignore-end -->
 
+#### zipN
+
+Zips given arrays
+
+##### Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(...xs: any[][]) => any[][]
+```
+<!-- prettier-ignore-end -->
+
+##### Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+zipN([1, 2, 3], [4, 5, 6]); // ⇒ [[1, 4], [2, 5], [3, 6]]
+```
+
+```javascript
+zipN([1, 2, 3], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+```
+
+```javascript
+zipN([1, 2], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7],[2, 5, 8]]
+```
+<!-- prettier-ignore-end -->
+
 #### zipWith
 
 Zips given arrays together with the given function.

array/README.md

@@ -552,6 +552,34 @@ Zips given arrays together into pairs.
 ```
 <!-- prettier-ignore-end -->
 
+# zipN
+
+Zips given arrays
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(...xs: any[][]) => any[][]
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+zipN([1, 2, 3], [4, 5, 6]); // ⇒ [[1, 4], [2, 5], [3, 6]]
+```
+
+```javascript
+zipN([1, 2, 3], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+```
+
+```javascript
+zipN([1, 2], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7],[2, 5, 8]]
+```
+<!-- prettier-ignore-end -->
+
 # zipWith
 
 Zips given arrays together with the given function.

array/index.js

@@ -39,6 +39,7 @@ import sum from "./sum.js";
 import take from "./take.js";
 import unique from "./unique.js";
 import zip from "./zip.js";
+import zipN from "./zipN.js";
 import zipWith from "./zipWith.js";
 
 export {
@@ -83,6 +84,7 @@ export {
   take,
   unique,
   zip,
+  zipN,
   zipWith
 };
 
@@ -128,5 +130,6 @@ export default {
   take,
   unique,
   zip,
+  zipN,
   zipWith
 };

array/index.ts

@@ -39,6 +39,7 @@ import sum from "./sum";
 import take from "./take";
 import unique from "./unique";
 import zip from "./zip";
+import zipN from "./zipN";
 import zipWith from "./zipWith";
 
 export {
@@ -83,6 +84,7 @@ export {
   take,
   unique,
   zip,
+  zipN,
   zipWith
 };
 
@@ -128,5 +130,6 @@ export default {
   take,
   unique,
   zip,
+  zipN,
   zipWith
 };

array/zipN.js

@@ -0,0 +1,7 @@
+export default (...xs) => {
+  const [head = [], ...tail] = xs;
+
+  return head.map((value, index) =>
+    tail.reduce((x, xs) => [...x, xs[index]], [value])
+  );
+};

array/zipN.json

@@ -0,0 +1,20 @@
+{
+  "name": "zipN",
+  "description": "Zips given arrays",
+  "signature": "(...xs: any[][]) => any[][]",
+  "examples": [
+    {
+      "language": "javascript",
+      "content": "zipN([1, 2, 3], [4, 5, 6]); // ⇒ [[1, 4], [2, 5], [3, 6]]"
+    },
+    {
+      "language": "javascript",
+      "content": "zipN([1, 2, 3], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7], [2, 5, 8], [3, 6, 9]]"
+    },
+    {
+      "language": "javascript",
+      "content": "zipN([1, 2], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7],[2, 5, 8]]"
+    }
+  ],
+  "questions": ["TODO: List questions that may this function answers."]
+}

array/zipN.md

@@ -0,0 +1,27 @@
+# zipN
+
+Zips given arrays
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(...xs: any[][]) => any[][]
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+zipN([1, 2, 3], [4, 5, 6]); // ⇒ [[1, 4], [2, 5], [3, 6]]
+```
+
+```javascript
+zipN([1, 2, 3], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+```
+
+```javascript
+zipN([1, 2], [4, 5, 6], [7, 8, 9]); // ⇒ [[1, 4, 7],[2, 5, 8]]
+```
+<!-- prettier-ignore-end -->

array/zipN.test.ts

@@ -0,0 +1,69 @@
+/* eslint-env jest */
+// @ts-ignore ambiguous import
+import zipN from "./zipN.ts";
+
+describe("zip", () => {
+  it("should zip with pair constructor", () => {
+    expect(zipN([1, 2, 3], [4, 5, 6])).toEqual([
+      [1, 4],
+      [2, 5],
+      [3, 6]
+    ]);
+  });
+
+  it("should zip up to the left arrays length", () => {
+    expect(zipN([1, 2, 3, 4, 5, 7], [4, 5, 6])).toEqual([
+      [1, 4],
+      [2, 5],
+      [3, 6],
+      [4, undefined],
+      [5, undefined],
+      [7, undefined]
+    ]);
+
+    expect(zipN([1, 2, 3], [4, 5, 6, 4, 5, 7])).toEqual([
+      [1, 4],
+      [2, 5],
+      [3, 6]
+    ]);
+  });
+
+  it("should return the wrapped elements of the source array when only one array is given", () => {
+    expect(zipN([1, 2])).toEqual([[1], [2]]);
+  });
+
+  it("should return an empty array when the given array is empty", () => {
+    expect(zipN([])).toEqual([]);
+  });
+
+  it("should return an empty array when the given nothing", () => {
+    expect(zipN()).toEqual([]);
+  });
+
+  it("should zip three arrays with the same lengths", () => {
+    expect(zipN([1, 2, 3], [4, 5, 6], [7, 8, 9])).toEqual([
+      [1, 4, 7],
+      [2, 5, 8],
+      [3, 6, 9]
+    ]);
+  });
+
+  it("should zip three arrays with different lengths", () => {
+    expect(zipN([1, 2, 3], [4, 5, 6], [7, 8])).toEqual([
+      [1, 4, 7],
+      [2, 5, 8],
+      [3, 6, undefined]
+    ]);
+
+    expect(zipN([1, 2, 3], [4, 5], [7, 8, 9])).toEqual([
+      [1, 4, 7],
+      [2, 5, 8],
+      [3, undefined, 9]
+    ]);
+
+    expect(zipN([1, 2], [4, 5, 6], [7, 8, 9])).toEqual([
+      [1, 4, 7],
+      [2, 5, 8]
+    ]);
+  });
+});

array/zipN.ts

@@ -0,0 +1,7 @@
+export default (...xs: any[][]) => {
+  const [head = [], ...tail] = xs;
+
+  return head.map((value, index) =>
+    tail.reduce((x, xs) => [...x, xs[index]], [value])
+  );
+};