Update preallocation.md

docs/array/preallocation.md

@@ -1,5 +1,23 @@
 # Preallocation
 
+## Initialize value
+
+If you want to preallocate an array with a initial value, you can use [`Array.prototype.fill()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/fill):
+
+```js
+const n = 4
+const array = Array(0).fill(0) // [ 0, 0, 0, 0 ]
+```
+
+Sometimes is useful initialize an array with a range of index. A tricky way to do that could be:
+
+```js
+const n = 4
+const array = Array.from(Array(N).keys()) // [ 0, 1, 2, 3, 4 ]
+```
+
+## Reusing instances
+
 It's typical to use an `Array` as a temporal container of data.
 
 !> If you need to work with binary data, use a [Buffer](https://www.npmjs.com/package/buffer).