Sum of Root To Leaf Binary Numbers

# 1022. Sum of Root To Leaf Binary Numbers

A sentence is a string of single-space separated words where each word consists only of path represents a binary number starting with the most significant bit.

For example, if the path is 0 -> 1 -> 1 -> 0 -> 1, then this could represent 01101 in binary, which is 13.
For all leaves in the tree, consider the numbers represented by the path from the root to that leaf. Return the sum of these numbers.

The test cases are generated so that the answer fits in a 32-bits integer.

### Example 1:
```
Input: root = [1,0,1,0,1,0,1]
Output: 22
Explanation: (100) + (101) + (110) + (111) = 4 + 5 + 6 + 7 = 22
```

### Example 2:
```
Input: root = [0]
Output: 0
 ```

Constraints:
```
The number of nodes in the tree is in the range [1, 1000].
Node.val is 0 or 1.
```

/**
 * 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
 * @return {number}
 */
 var sumRootToLeaf = function(root) {
    let sum = 0;
    const dfs = (node, numStr) => {
        if (!node) {
            return;
        }
        
        numStr += node.val;
        if (!node.left && !node.right) {
            sum += parseInt(numStr, 2);
            return;
        }        

        dfs(node.left, numStr);
        dfs(node.right, numStr);
    };

    dfs(root, '');
    return sum;
};