feat: add js solution to lc problem: No.1929.Concatenation of Array (#509)

Author: zhaocchen

solution/1900-1999/1929.Concatenation of Array/README.md

@@ -82,6 +82,20 @@ class Solution {
 }
 ```
 
+### **JavaScript**
+
+```js
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var getConcatenation = function(nums) {
+    let ans = nums.slice();
+    ans.splice(nums.length, 0, ...nums);
+    return ans;
+};
+```
+
 ### **C++**
 
 ```cpp

solution/1900-1999/1929.Concatenation of Array/README_EN.md

@@ -67,6 +67,20 @@ class Solution {
 }
 ```
 
+### **JavaScript**
+
+```js
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var getConcatenation = function(nums) {
+    let ans = nums.slice();
+    ans.splice(nums.length, 0, ...nums);
+    return ans;
+};
+```
+
 ### **C++**
 
 ```cpp

solution/1900-1999/1929.Concatenation of Array/Solution.js

@@ -0,0 +1,9 @@
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+ var getConcatenation = function(nums) {
+    let ans = nums.slice();
+    ans.splice(nums.length, 0, ...nums);
+    return ans;
+};