添加20. 有效的括号JavaScript版本

problems/0020.有效的括号.md

@@ -271,6 +271,23 @@ var isValid = function (s) {
   }
   return stack.length === 0;
 };
+// 简化版本
+var isValid = function(s) {
+    const stack = [], 
+        map = {
+            "(":")",
+            "{":"}",
+            "[":"]"
+        };
+    for(const x of s) {
+        if(x in map) {
+            stack.push(x);
+            continue;
+        };
+        if(map[stack.pop()] !== x) return false;
+    }
+    return !stack.length;
+};
 ```