Serialize and Deserialize Binary Tree

Problem statement

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

Clarification: The input/output format is the same as how LeetCode serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Example 1:

Input: root = [1,2,3,null,null,4,5]Output: [1,2,3,null,null,4,5]

Example 2:

Input: root = []Output: []

Constraints:

• The number of nodes in the tree is in the range [0, 104].
• -1000 <= Node.val <= 1000

My solution

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */

/**
 * Encodes a tree to a single string.
 *
 * @param {TreeNode} root
 * @return {string}
 */
var serialize = function(root) {
    const nodes = []
    
    function dfs(node) {
        if (!node) {
            nodes.push("$")
        } else {
            nodes.push(node.val)
            dfs(node.left)
            dfs(node.right)
        }
    }
    
    dfs(root)
    return nodes.join(",")
};

/**
 * Decodes your encoded data to tree.
 *
 * @param {string} data
 * @return {TreeNode}
 */
var deserialize = function(data) {
    if (!data || data.length === 0) {
        return null
    }
    
    function dfs(arr) {
        if (arr.length === 0) {
            return null
        }
        const value = arr.shift()
        if (value === "$") {
            return null
        }
        const node = new TreeNode(value);
        node.left = dfs(arr);
        node.right = dfs(arr);
        
        return node;
    }
    
    return dfs(data.split(","))
};

/**
 * Your functions will be called as such:
 * deserialize(serialize(root));
 */