First Unique Character in a String

Author: w2xi

README.md

@@ -13,4 +13,5 @@
 |189|[轮转数组](https://leetcode-cn.com/problems/rotate-array/)|[JavaScript](./algorithms/rotate-array.js)|Medium|
 |344|[反转字符串](https://leetcode-cn.com/problems/reverse-string/)|[JavaScript](./algorithms/reverse-string.js)|Easy|
 |349|[两个数组的交集](https://leetcode-cn.com/problems/intersection-of-two-arrays/)|[JavaScript](./algorithms/intersection-of-two-arrays.js)|Easy|
-|350|[两个数组的交集 II](https://leetcode-cn.com/problems/intersection-of-two-arrays-ii/)|[JavaScript](./algorithms/intersection-of-two-arrays-ii.js)|Easy|
+|350|[两个数组的交集 II](https://leetcode-cn.com/problems/intersection-of-two-arrays-ii/)|[JavaScript](./algorithms/intersection-of-two-arrays-ii.js)|Easy|
+|387|[字符串中的第一个唯一字符](https://leetcode-cn.com/problems/first-unique-character-in-a-string/)|[JavaScript](./algorithms/first-unique-character-in-a-string.js)|Easy|

algorithms/first-unique-character-in-a-string.js

@@ -0,0 +1,28 @@
+// 方法一：Map(映射)
+
+/**
+ * 字符串中的第一个唯一字符
+ * @param {string} s
+ * @return {number}
+ */
+var firstUniqChar = function (s) {
+  const map = new Map();
+
+  for (let i = 0; i < s.length; i++) {
+    let char = s[i];
+
+    if (map.has(char)) {
+      let count = map.get(char);
+      map.set(char, count + 1);
+    } else {
+      map.set(char, 1);
+    }
+  }
+  for (let i = 0; i < s.length; i++) {
+    if (map.get(s[i]) === 1) {
+      return i;
+    }
+  }
+
+  return -1;
+};