深度优先、广度优先创建n叉树

function makeTree(layer) {
    const root = {};
    makeNode(root, layer);
    return root;
}

function makeNode(node, layer, keys = ['left', 'right']) {

    if (!--layer) {
        keys.forEach((key) => {
            node[key] = null;
        })
        return;
    }
    
    keys.forEach((key) => {
        node[key] = {};
    });
    
    keys.forEach((key) => {
        makeNode(node[key], layer);
    });

}

function makeTree(layer, keys = ['left', 'right']) {
    if (!layer) {
        return null;
    }
    layer--;
    const node = {};
     keys.forEach((key) => {
        node[key] = makeTree(layer);
    });
    
    return node;
}

function makeBinaryTree(layer = 4) {
   
   function Node(opts) {
    return opts;
   }
   
   const root = {value: 0, layer: 0};
   let queue = [root];
   let current;
   while(current = queue.shift()) {
    
    if (current.layer == layer) {
     return root;
    }
    current.left = new Node({value: 0, layer: current.layer + 1});
    current.right = new Node({value: 1, layer: current.layer + 1});
    queue.push(current.left);
    queue.push(current.right);
   }

  }