Deep flatten and housekeeping

Changed original flatten to be named deepFlatten, added normal flatten, improved some other snippets.

snippets/count-occurrences-of-a-value-in-array.md

@@ -3,6 +3,6 @@
 Use `reduce()` to increment a counter each time you encounter the specific value inside the array.
 
 ```js
-const countOccurrences = (arr, value) => arr.reduce((a, v) => v===value ? a + 1 : a + 0, 0);
+const countOccurrences = (arr, value) => arr.reduce((a, v) => v === value ? a + 1 : a + 0, 0);
 // countOccurrences([1,1,2,1,2,3], 1) -> 3
 ```

snippets/deep-flatten-array.md

@@ -0,0 +1,10 @@
+### Deep flatten array
+
+Use recursion.
+Use `reduce()` to get all elements that are not arrays, flatten each element that is an array.
+
+```js
+const deepFlatten = arr =>
+  arr.reduce( (a, v) => a.concat( Array.isArray(v) ? flatten(v) : v ), []);
+// deepFlatten([1,[2],[[3],4],5]) -> [1,2,3,4,5]
+```

snippets/escape-regular-expression.md

@@ -3,7 +3,6 @@
 Use `replace()` to escape special characters.
 
 ```js
-const escapeRegExp = s =>
-  s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+const escapeRegExp = str => str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
 // escapeRegExp('(test)') -> \\(test\\)
 ```

snippets/flatten-array.md

@@ -1,10 +1,8 @@
 ### Flatten array
 
-Use recursion.
-Use `reduce()` to get all elements that are not arrays, flatten each element that is an array.
+Use `reduce()` to get all elements inside the array and `concat()` to flatten them.
 
 ```js
-const flatten = arr =>
-  arr.reduce( (a, v) => a.concat( Array.isArray(v) ? flatten(v) : v ), []);
-// flatten([1,[2],[[3],4],5]) -> [1,2,3,4,5]
+const flatten = arr => arr.reduce( (a, v) => a.concat(v), []);
+// flatten([1,[2],3,4) -> [1,2,3,4]
 ```