1325-删除给定值的叶子节点

var removeLeafNodes = function(root, target) {
    var dfs = function (root) {
        if (root.left) {
            root.left = dfs(root.left)
        }
        if (root.right) {
            root.right = dfs(root.right)
        }
        if (!root.left && !root.right) {
            if (root.val === target)  {
                root = null            }
        }
        return root    }
    var dummy = new TreeNode(0)
    dummy.left = root    dfs(dummy)
    return dummy.left};