add js solution for leecode 3 and 7

Author: swiftwind0405

README.md

@@ -370,7 +370,7 @@
 |56|[Merge Intervals](https://leetcode.com/problems/merge-intervals/)| |Hard|
 |55|[Jump Game](https://leetcode.com/problems/jump-game/)| |Medium|
 |54|[Spiral Matrix](https://leetcode.com/problems/spiral-matrix/)| |Medium|
-|53|[Maximum Subarray](https://leetcode.com/problems/maximum-subarray/)| |Medium|
+|53|[Maximum Subarray](https://leetcode.com/problems/maximum-subarray/)| [js](./algorithms/maximumSubarray/maximumSubarray.js) |Medium|
 |52|[N-Queens II](https://leetcode.com/problems/n-queens-ii/)| |Hard|
 |51|[N-Queens](https://leetcode.com/problems/n-queens/)| |Hard|
 |50|["Pow(x, n)"](https://leetcode.com/problems/powx-n/)| |Medium|
@@ -416,7 +416,7 @@
 |10|[Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/)| |Hard|
 |9|[Palindrome Number](https://leetcode.com/problems/palindrome-number/)| |Easy|
 |8|[String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/)| |Easy|
-|7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/)| |Easy|
+|7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/)| [js](./algorithms/reverseInteger/reverseInteger.js) |Easy|
 |6|[ZigZag Conversion](https://leetcode.com/problems/zigzag-conversion/)| |Easy|
 |5|[Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)| |Medium|
 |4|[Median of Two Sorted Arrays](https://leetcode.com/problems/median-of-two-sorted-arrays/)| |Hard|

algorithms/maximumSubarray/maximumSubarray.js

@@ -0,0 +1,12 @@
+var maxSubArray = function(nums) {
+    // 初始值为0,最大值为第一个无素。
+    let pre = 0, maxAns = nums[0];
+    nums.forEach((x) => {
+        // 前一个元素加到当前元素上，取较大值
+        pre = Math.max(pre + x, x);
+        // 取结果的最大值
+        maxAns = Math.max(maxAns, pre);
+        console.log(pre, maxAns)
+    });
+    return maxAns;
+};

algorithms/reverseInteger/reverseInteger.js

@@ -0,0 +1,8 @@
+var reverse = function(x) {
+    let result = 0;
+    while(x !== 0) {
+        result = result * 10 + x % 10;
+        x = (x / 10) | 0;
+    }
+    return (result | 0) === result ? result : 0;
+};