Travis build: 1168

README.md

@@ -768,19 +768,26 @@ filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1,3,5]
 
 ### flatten
 
-Flattens an array.
+Flattens an array up to the specified depth.
 
-Use a new array, `Array.concat()` and the spread operator (`...`) to cause a shallow denesting of any contained arrays.
+Use recursion, decrementing `depth` by 1 for each level of depth.
+Use `Array.reduce()` and `Array.concat()` to merge elements or arrays.
+Base case, for `depth` equal to `1` stops recursion.
+Omit the second argument, `depth` to flatten only to a depth of `1` (single flatten).
 
 ```js
-const flatten = arr => [].concat(...arr);
+const flatten = (arr, depth = 1) =>
+  depth != 1
+    ? arr.reduce((a, v) => a.concat(Array.isArray(v) ? flatten(v, depth - 1) : v), [])
+    : arr.reduce((a, v) => a.concat(v), []);
 ```
 
 <details>
 <summary>Examples</summary>
 
 ```js
-flatten([1, [2], 3, 4]); // [1,2,3,4]
+flatten([1, [2], 3, 4]); // [1, 2, 3, 4]
+flatten([1, [2, [3, [4, 5], 6], 7], 8], 2); // [1, 2, 3, [4, 5], 6, 7, 8]
 ```
 
 </details>
@@ -5201,6 +5208,7 @@ const httpPost = (url, callback, data = null, err = console.error) => {
 
 
 
+
 const newPost = {
   "userId": 1,
   "id": 1337,