feat: 🎸 add more reduce sample

arrays/reducing.js

@@ -24,9 +24,34 @@ function flattenArrayObjectMethod3(arr) {
   return arr.reduce((obj, current) => ({...obj, [current.key]: current.value}), {});
 }
 
+function mapping(list, fn) {
+  return list.reduce( (newList, item) => newList.concat(fn(item)), []);
+}
+
+function findMin(arr) {
+  return arr.reduce((min, curr) => curr < min ? curr : min, arr[0]);
+}
+
+function findMax(arr) {
+  return arr.reduce((max, curr) => curr > max ? curr : max, arr[0]);
+}
+
+function findUniqueValues(arr) {
+  return arr.reduce((acc, curr) => {
+    if (!acc.includes(curr)) {
+      acc.push(curr);
+    }
+    return acc;
+  }, []);
+}
+
 module.exports = {
   sum,
   flattenArrayObjectMethod1,
   flattenArrayObjectMethod2,
-  flattenArrayObjectMethod3
+  flattenArrayObjectMethod3,
+  mapping,
+  findMin,
+  findMax,
+  findUniqueValues
 };

arrays/reducing.test.js

@@ -1,4 +1,13 @@
-const { sum, flattenArrayObjectMethod1, flattenArrayObjectMethod2, flattenArrayObjectMethod3 } = require('./reducing');
+const { 
+  sum, 
+  flattenArrayObjectMethod1, 
+  flattenArrayObjectMethod2, 
+  flattenArrayObjectMethod3,
+  mapping,
+  findMin,
+  findMax,
+  findUniqueValues
+} = require('./reducing');
 
 describe('sum', () => {
   const arr = [1, 2, 3];
@@ -34,4 +43,34 @@ describe('flatten array of objects', () => {
   it('flattenArrayObjectMethod3 should flatten an array of objects', () => {
     expect(flattenArrayObjectMethod3(arr)).toEqual(expected);
   });
+});
+
+
+describe('map using reduce', () => {
+  const arr = [1, 2, 3];
+  const fn = (x) => x * 2;
+
+  it('should map an array', () => {
+    expect(mapping(arr, fn)).toEqual([2, 4, 6]);
+  });
+});
+
+describe('find min and max using reduce', () => {
+  const arr = [1, 2, 3, 4, 5];
+
+  it('should find the min', () => {
+    expect(findMin(arr)).toEqual(1);
+  });
+
+  it('should find the max', () => {
+    expect(findMax(arr)).toEqual(5);
+  });
+});
+
+describe('find unique values using reduce', () => {
+  const arr = [1, 1, 2, 3, 3, 4, 5];
+
+  it('should find the unique values', () => {
+    expect(findUniqueValues(arr)).toEqual([1, 2, 3, 4, 5]);
+  });
 });