feat: add js solution to lc problem: No.270

solution/0200-0299/0270.Closest Binary Search Tree Value/README.md

@@ -144,6 +144,40 @@ var closestValue = function (root, target) {
 };
 ```
 
+```js
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {number} target
+ * @return {number}
+ */
+var closestValue = function (root, target) {
+    let mi = Infinity,
+        ans = root.val;
+    const dfs = (root, target) => {
+        if (!root) {
+            return;
+        }
+        dfs(root.left, target);
+        const t = Math.abs(root.val - target);
+        if (t < mi) {
+            mi = t;
+            ans = root.val;
+        }
+        dfs(root.right, target);
+    };
+    dfs(root, target);
+    return ans;
+};
+```
+
 ### **C++**
 
 ```cpp

solution/0200-0299/0270.Closest Binary Search Tree Value/README_EN.md

@@ -134,6 +134,40 @@ var closestValue = function (root, target) {
 };
 ```
 
+```js
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {number} target
+ * @return {number}
+ */
+var closestValue = function (root, target) {
+    let mi = Infinity,
+        ans = root.val;
+    const dfs = (root, target) => {
+        if (!root) {
+            return;
+        }
+        dfs(root.left, target);
+        const t = Math.abs(root.val - target);
+        if (t < mi) {
+            mi = t;
+            ans = root.val;
+        }
+        dfs(root.right, target);
+    };
+    dfs(root, target);
+    return ans;
+};
+```
+
 ### **C++**
 
 ```cpp