Add solution #2124

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,761 LeetCode solutions in JavaScript
+# 1,762 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1626,6 +1626,7 @@
 2120|[Execution of All Suffix Instructions Staying in a Grid](./solutions/2120-execution-of-all-suffix-instructions-staying-in-a-grid.js)|Medium|
 2121|[Intervals Between Identical Elements](./solutions/2121-intervals-between-identical-elements.js)|Medium|
 2122|[Recover the Original Array](./solutions/2122-recover-the-original-array.js)|Hard|
+2124|[Check if All A's Appears Before All B's](./solutions/2124-check-if-all-as-appears-before-all-bs.js)|Easy|
 2127|[Maximum Employees to Be Invited to a Meeting](./solutions/2127-maximum-employees-to-be-invited-to-a-meeting.js)|Hard|
 2129|[Capitalize the Title](./solutions/2129-capitalize-the-title.js)|Easy|
 2130|[Maximum Twin Sum of a Linked List](./solutions/2130-maximum-twin-sum-of-a-linked-list.js)|Medium|

solutions/2124-check-if-all-as-appears-before-all-bs.js

@@ -0,0 +1,23 @@
+/**
+ * 2124. Check if All A's Appears Before All B's
+ * https://leetcode.com/problems/check-if-all-as-appears-before-all-bs/
+ * Difficulty: Easy
+ *
+ * Given a string s consisting of only the characters 'a' and 'b', return true if every 'a' appears
+ * before every 'b' in the string. Otherwise, return false.
+ */
+
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var checkString = function(s) {
+  let seen = false;
+
+  for (const char of s) {
+    if (char === 'b') seen = true;
+    else if (seen) return false;
+  }
+
+  return true;
+};