Add array/insert method (#37)

* Add insert method

* Update after code review

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

Author: 2 people

README.md

@@ -203,6 +203,32 @@ Flattens the nested arrays by a single level.
 ```
 <!-- prettier-ignore-end -->
 
+#### insert
+
+Inserts the given item to the array at a specific index.
+
+##### Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(
+  index: number
+) => (item: any) => ([...xs]: any[]) => any[]
+```
+<!-- prettier-ignore-end -->
+
+##### Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+insert(0)('d')(['a', 'b', 'c']); // ⇒ ['d', 'a', 'b', 'c']
+```
+
+```javascript
+insert(1)('d')(['a', 'b', 'c']); // ⇒ ['a', 'd', 'b', 'c']
+```
+<!-- prettier-ignore-end -->
+
 #### intersection
 
 Finds common items between both arrays.

array/README.md

@@ -186,6 +186,32 @@ Flattens the nested arrays by a single level.
 ```
 <!-- prettier-ignore-end -->
 
+# insert
+
+Inserts the given item to the array at a specific index.
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(
+  index: number
+) => (item: any) => ([...xs]: any[]) => any[]
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+insert(0)('d')(['a', 'b', 'c']); // ⇒ ['d', 'a', 'b', 'c']
+```
+
+```javascript
+insert(1)('d')(['a', 'b', 'c']); // ⇒ ['a', 'd', 'b', 'c']
+```
+<!-- prettier-ignore-end -->
+
 # intersection
 
 Finds common items between both arrays.

array/index.js

@@ -11,6 +11,7 @@ import find from "./find.js";
 import first from "./first.js";
 import flatMap from "./flatMap.js";
 import flatten from "./flatten.js";
+import insert from "./insert.js";
 import intersection from "./intersection.js";
 import is from "./is.js";
 import last from "./last.js";
@@ -53,6 +54,7 @@ export {
   first,
   flatMap,
   flatten,
+  insert,
   intersection,
   is,
   last,
@@ -96,6 +98,7 @@ export default {
   first,
   flatMap,
   flatten,
+  insert,
   intersection,
   is,
   last,

array/index.ts

@@ -11,6 +11,7 @@ import find from "./find";
 import first from "./first";
 import flatMap from "./flatMap";
 import flatten from "./flatten";
+import insert from "./insert";
 import intersection from "./intersection";
 import is from "./is";
 import last from "./last";
@@ -53,6 +54,7 @@ export {
   first,
   flatMap,
   flatten,
+  insert,
   intersection,
   is,
   last,
@@ -96,6 +98,7 @@ export default {
   first,
   flatMap,
   flatten,
+  insert,
   intersection,
   is,
   last,

array/insert.js

@@ -0,0 +1,5 @@
+export default index => item => ([...xs]) => {
+  xs.splice(index, 0, item);
+
+  return xs;
+};

array/insert.json

@@ -0,0 +1,16 @@
+{
+  "name": "insert",
+  "description": "Inserts the given item to the array at a specific index.",
+  "signature": "(\n  index: number\n) => (item: any) => ([...xs]: any[]) => any[]",
+  "examples": [
+    {
+      "language": "javascript",
+      "content": "insert(0)('d')(['a', 'b', 'c']); // ⇒ ['d', 'a', 'b', 'c']"
+    },
+    {
+      "language": "javascript",
+      "content": "insert(1)('d')(['a', 'b', 'c']); // ⇒ ['a', 'd', 'b', 'c']"
+    }
+  ],
+  "questions": ["TODO: List questions that may this function answer."]
+}

array/insert.md

@@ -0,0 +1,25 @@
+# insert
+
+Inserts the given item to the array at a specific index.
+
+## Type signature
+
+<!-- prettier-ignore-start -->
+```typescript
+(
+  index: number
+) => (item: any) => ([...xs]: any[]) => any[]
+```
+<!-- prettier-ignore-end -->
+
+## Examples
+
+<!-- prettier-ignore-start -->
+```javascript
+insert(0)('d')(['a', 'b', 'c']); // ⇒ ['d', 'a', 'b', 'c']
+```
+
+```javascript
+insert(1)('d')(['a', 'b', 'c']); // ⇒ ['a', 'd', 'b', 'c']
+```
+<!-- prettier-ignore-end -->

array/insert.test.ts

@@ -0,0 +1,21 @@
+/* eslint-env jest */
+// @ts-ignore ambiguous import
+import insert from "./insert.ts";
+
+describe("insert", () => {
+  it("should insert item to the array on the second position", () => {
+    expect(insert(1)("d")(["a", "b", "c"])).toEqual(["a", "d", "b", "c"]);
+    expect(insert(-2)("d")(["a", "b", "c"])).toEqual(["a", "d", "b", "c"]);
+  });
+
+  it("should insert item to the array on the first position", () => {
+    expect(insert(0)("b")(["a"])).toEqual(["b", "a"]);
+    expect(insert(-1)("b")(["a"])).toEqual(["b", "a"]);
+  });
+
+  it("should insert item to empty array on the first position", () => {
+    expect(insert(10)("a")([])).toEqual(["a"]);
+    expect(insert(0)("a")([])).toEqual(["a"]);
+    expect(insert(-10)("a")([])).toEqual(["a"]);
+  });
+});

array/insert.ts

@@ -0,0 +1,5 @@
+export default (index: number) => (item: any) => ([...xs]: any[]) => {
+  xs.splice(index, 0, item);
+
+  return xs;
+};