二叉树的先中后序遍历-JS递归实现

const bt = {
    val: 1,
    left: {
        val: 2,
        left: {
            val: 4,
            left: null,
            right: null,
        },
        right: {
            val: 5,
            left: null,
            right: null,
        },
    },
    right: {
        val: 3,
        left: {
            val: 6,
            left: null,
            right: null,
        },
        right: {
            val: 7,
            left: null,
            right: null,
        },
    },
};
//先序遍历
const preorder = (root) => {
    if(!root) {return;}
    console.log(root.val);
    preorder(root.left);
    preorder(root.right);
};

preorder(bt);

//中序遍历
const inorder = (root) => {
    if(!root) {return;}
    inorder(root.left);
    console.log(root.val);
    inorder(root.right);
};
inorder(bt);

//后序遍历
const postorder = (root) => {
    if(!root) {return;}
    postorder(root.left);
    postorder(root.right);
    console.log(root.val);
};

postorder(bt);