Add solution for problem 1146 (#128)

* Add solution for problem 1146 in Javascript

* Add js file

Author: ltp88

README.md

@@ -1061,6 +1061,7 @@ _If you like this project, please leave me a star._ ★
 |1179|[Reformat Department Table](https://leetcode.com/problems/reformat-department-table/)|[Solution](../master/database/_1179.sql) |  | Easy |
 |1173|[Immediate Food Delivery I](https://leetcode.com/problems/immediate-food-delivery-i/)|[Solution](../master/database/_1173.sql) |  | Easy |
 |1148|[Article Views I](https://leetcode.com/problems/article-views-i/)|[Solution](../master/database/_1148.sql) |  | Easy |
+|1146|[Snapshot Array](https://leetcode.com/problems/snapshot-array/)|[Javascript](./javascript/_1146.js)| | Easy |
 |1141|[User Activity for the Past 30 Days I](https://leetcode.com/problems/user-activity-for-the-past-30-days-i/)|[Solution](../master/database/_1141.sql) |  | Easy |
 |1084|[Sales Analysis III](https://leetcode.com/problems/sales-analysis-iii/)|[Solution](../master/database/_1084.sql) |  | Easy |
 |1083|[Sales Analysis II](https://leetcode.com/problems/sales-analysis-ii/)|[Solution](../master/database/_1083.sql) |  | Easy |

javascript/_1146.js

@@ -0,0 +1,48 @@
+/**
+ * Author: Phuong Lam
+ */
+
+/**
+ * @param {number} length
+ */
+var SnapshotArray = function (length) {
+  this.changes = {}
+  this.snapShots = []
+}
+
+/**
+ * @param {number} index
+ * @param {number} val
+ * @return {void}
+ */
+SnapshotArray.prototype.set = function (index, val) {
+  this.changes[index] = val
+}
+
+/**
+ * @return {number}
+ */
+SnapshotArray.prototype.snap = function () {
+  this.snapShots.push(this.changes)
+  this.changes = {}
+  return this.snapShots.length - 1
+}
+
+/**
+ * @param {number} index
+ * @param {number} snap_id
+ * @return {number}
+ */
+SnapshotArray.prototype.get = function (index, snap_id) {
+  while (snap_id >= 0 && this.snapShots[snap_id][index] === undefined) snap_id--
+  if (snap_id >= 0) return this.snapShots[snap_id][index]
+  return 0
+}
+
+/**
+ * Your SnapshotArray object will be instantiated and called as such:
+ * var obj = new SnapshotArray(length)
+ * obj.set(index,val)
+ * var param_2 = obj.snap()
+ * var param_3 = obj.get(index,snap_id)
+ */