添加“20.有效的括号”Javascript版本

problems/0020.有效的括号.md

@@ -247,6 +247,32 @@ def is_valid(strs)
 end
 ```
 
+Javascript:
+```javascript
+var isValid = function (s) {
+  const stack = [];
+  for (let i = 0; i < s.length; i++) {
+    let c = s[i];
+    switch (c) {
+      case '(':
+        stack.push(')');
+        break;
+      case '[':
+        stack.push(']');
+        break;
+      case '{':
+        stack.push('}');
+        break;
+      default:
+        if (c !== stack.pop()) {
+          return false;
+        }
+    }
+  }
+  return stack.length === 0;
+};
+```
+
 
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 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)