feat: add solution of Climbing Stairs(070) with javascript.

Author: 钱毓婷

README.md

@@ -70,7 +70,7 @@
 | [067][067-question] | [Add Binary][067-tips]                                       | [Easy][E]   | [✅][067-java] | [✅][067-js] | [✅][067-kotlin] |
 | [068][068-question] | [Text Justification][068-tips]                               | [Hard][H]   | [✅][068-java] |              |                  |
 | [069][069-question] | [Sqrt(x)][069-tips]                                          | [Easy][E]   | [✅][069-java] | [✅][069-js] | [✅][069-kotlin] |
-| [070][070-question] | [Climbing Stairs][070-tips]                                  | [Easy][E]   | [✅][070-java] |              | [✅][070-kotlin] |
+| [070][070-question] | [Climbing Stairs][070-tips]                                  | [Easy][E]   | [✅][070-java] | [✅][070-js] | [✅][070-kotlin] |
 | [083][083-question] | [Remove Duplicates from Sorted List][083-tips]               | [Easy][E]   | [✅][083-java] |              | [✅][083-kotlin] |
 | [088][088-question] | [Merge Sorted Array][088-tips]                               | [Easy][E]   | [✅][088-java] |              | [✅][088-kotlin] |
 | [100][100-question] | [Same Tree][100-tips]                                        | [Easy][E]   | [✅][100-java] |              | [✅][100-kotlin] |
@@ -376,6 +376,7 @@
 [066-js]: ./src/_066/Solution.js
 [067-js]: ./src/_067/Solution.js
 [069-js]: ./src/_069/Solution.js
+[070-js]: ./src/_070/Solution.js
 [226-js]: ./src/_226/Solution.js
 [561-js]: ./src/_561/Solution.js
 [643-js]: ./src/_643/Solution.js

src/_070/Solution.js

@@ -0,0 +1,16 @@
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function(n) {
+    if(n == 1) {return 1}
+    if(n == 2) {return 2}
+    
+    var step1 = 1, step2 = 2, x;
+    for(var i = 2 ; i < n; i++) {
+        x = step2
+        step2 += step1
+        step1 = x
+    }
+    return step2
+};

tips/070/README.md

@@ -73,6 +73,24 @@ class Solution {
 }
 ```
 
+```JavaScript
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function(n) {
+    if(n == 1) {return 1}
+    if(n == 2) {return 2}
+    
+    var step1 = 1, step2 = 2, x;
+    for(var i = 2 ; i < n; i++) {
+        x = step2
+        step2 += step1
+        step1 = x
+    }
+    return step2
+};
+```
 ## 结语
 
 如果你同我们一样热爱数据结构、算法、LeetCode，可以关注我们 GitHub 上的 LeetCode 题解：[LeetCode-Solution][ls]