add js soultion for leetcode 70

Author: swiftwind0405

README.md

@@ -353,7 +353,7 @@
 |73|[Set Matrix Zeroes](https://leetcode.com/problems/set-matrix-zeroes/)| |Medium|
 |72|[Edit Distance](https://leetcode.com/problems/edit-distance/)| |Hard|
 |71|[Simplify Path](https://leetcode.com/problems/simplify-path/)| |Medium|
-|70|[Climbing Stairs](https://leetcode.com/problems/climbing-stairs/)| |Easy|
+|70|[Climbing Stairs](https://leetcode.com/problems/climbing-stairs/)| [js](./algorithms/climbingStairs/climbingStairs.js), |Easy|
 |69|[Sqrt(x)](https://leetcode.com/problems/sqrtx/)| |Medium|
 |68|[Text Justification](https://leetcode.com/problems/text-justification/)| |Hard|
 |67|[Add Binary](https://leetcode.com/problems/add-binary/)| |Easy|

algorithms/climbingStairs/climbingStairs.js

@@ -0,0 +1,9 @@
+var climbStairs = function(n) {
+    let p = 0, q = 0, r = 1;
+    for (let i = 1; i <= n; i++) {
+        p = q;
+        q = r;
+        r = p + q;
+    }
+    return r;
+};