請看下圖的動態呈現。

簡而言之，深度優先搜尋法會先從root節點開始，先由左側的子節點往下找有無子節點，如果有就繼續往下找，如果沒有就回到上一層節點，找尋有無其他子節點，依此類推。

程式碼如下:

function Node(data) {
  this.data = data;
  this.parent = null;
  this.children = [];
}

function Tree(data) {
  var node = new Node(data);
  this._root = node;
}

Tree.prototype.traverseDF = function(callback) {
  (function recurse(currentNode) {
    callback(currentNode); 
    for (var i = 0, length = currentNode.children.length; i < length; i++) {
      recurse(currentNode.children[i]);
    }
  })(this._root);
};
const tree = new Tree('1');

tree._root.children.push(new Node('2'));
tree._root.children[0].parent = tree;

tree._root.children.push(new Node('5'));
tree._root.children[1].parent = tree;

tree._root.children[1].children.push(new Node('6'));
tree._root.children[1].children.push(new Node('8'));

tree._root.children[1].children[0].children.push(new Node('7'));

tree._root.children.push(new Node('9'));
tree._root.children[2].parent = tree;

tree._root.children[2].children.push(new Node('10'));

tree._root.children[0].children.push(new Node('3'));
tree._root.children[0].children[0].parent = tree._root.children[0];

tree._root.children[0].children[0].children.push(new Node('4'));
tree._root.children[0].children[0].children[0].parent = tree._root.children[0].children[0];

tree.traverseDF(function(node) {
  console.log(node.data)
});

程式碼