Function dfs

javascript/0513-find-bottom-left-tree-value.js:20–31

(node, level)

    let deepestLevel = -Infinity;

    const dfs = (node, level) => {
        if (!node.left && !node.right) {
            if (level > deepestLevel) {
                leftVal = node.val;
                deepestLevel = level;
            }
            return;
        }

        node.left && dfs(node.left, level + 1);
        node.right && dfs(node.right, level + 1);
    };

    dfs(root, 0);
    return leftVal;