Complete sorted union algorithm

Author: ahcode0919

src/fcc-intermediate-algorithms/fcc-intermediate-algorithms.md

@@ -13,6 +13,7 @@ From the Freecodecamp Javascript Certification Intermediate Algorithms module
 - [Search and Replace](#search-and-replace)
 - [DNA Pairing](#dna-pairing)
 - [Missing Letters](#missing-letters)
+- [Sorted Union](#sorted-union)
 
 #### Sum All Numbers In a Range
 
@@ -198,3 +199,24 @@ export function fearNotLetter(str) {
     return undefined;
 }
 ```
+
+#### Sorted Union
+
+Write a function that takes two or more arrays and returns a new array of unique values in the order of the original provided arrays.
+
+In other words, all values present from all arrays should be included in their original order, but with no duplicates in the final array.
+
+The unique numbers should be sorted by their original order, but the final array should not be sorted in numerical order.
+
+```javascript
+export function uniteUnique(...arr) {
+    return arr.reduce((union, subArray) => {
+        for (let num of subArray) {
+            if (union.indexOf(num) === -1) {
+                union.push(num);
+            }
+        }
+        return union;
+    }, []);
+}
+```

src/fcc-intermediate-algorithms/sorted_union.js

@@ -0,0 +1,10 @@
+export function uniteUnique(...arr) {
+    return arr.reduce((union, subArray) => {
+        for (let num of subArray) {
+            if (union.indexOf(num) === -1) {
+                union.push(num);
+            }
+        }
+        return union;
+    }, []);
+}

tests/fcc-intermediate-algorithms/sorted_union.test.js

@@ -0,0 +1,5 @@
+import { uniteUnique } from "../../src/fcc-intermediate-algorithms/sorted_union";
+
+test('should flatten arrays and remove duplicates', () => {
+    expect(uniteUnique([1,2], [2, 3])).toEqual([1, 2, 3])
+});