Merge pull request #532 from Chalarangelo/flatten-fix

[FIX: #525] Flatten fix

snippets/flatten.md

@@ -1,13 +1,20 @@
 ### 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), []);
 ```
 
 ```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]
 ```

test/flatten/flatten.js

@@ -1 +1,4 @@
-module.exports = flatten = arr => [].concat(...arr);
+module.exports = 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), []);

test/flatten/flatten.test.js

@@ -6,6 +6,7 @@ test('Testing flatten', (t) => {
 	//Please go to https://github.com/substack/tape
 	t.true(typeof flatten === 'function', 'flatten is a Function');
 	t.deepEqual(flatten([1, [2], 3, 4]), [1, 2, 3, 4], "Flattens an array");
+	t.deepEqual(flatten([1, [2, [3, [4, 5], 6], 7], 8], 2), [1, 2, 3, [4, 5], 6, 7, 8], "Flattens an array");
 	//t.deepEqual(flatten(args..), 'Expected');
 	//t.equal(flatten(args..), 'Expected');
 	//t.false(flatten(args..), 'Expected');

test/flattenDepth/flattenDepth.js

@@ -1,4 +0,0 @@
-module.exports = flattenDepth = (arr, depth = 1) =>
-depth != 1
-? arr.reduce((a, v) => a.concat(Array.isArray(v) ? flattenDepth(v, depth - 1) : v), [])
-: arr.reduce((a, v) => a.concat(v), []);

test/flattenDepth/flattenDepth.test.js

@@ -1,14 +0,0 @@
-const test = require('tape');
-const flattenDepth = require('./flattenDepth.js');
-
-test('Testing flattenDepth', (t) => {
-	//For more information on all the methods supported by tape
-	//Please go to https://github.com/substack/tape
-	t.true(typeof flattenDepth === 'function', 'flattenDepth is a Function');
-	t.deepEqual(flattenDepth([1, [2], 3, 4]), [1, 2, 3, 4], "Flattens an array up to the specified depth");
-	//t.deepEqual(flattenDepth(args..), 'Expected');
-	//t.equal(flattenDepth(args..), 'Expected');
-	//t.false(flattenDepth(args..), 'Expected');
-	//t.throws(flattenDepth(args..), 'Expected');
-	t.end();
-});