SOURCE

//深度优先遍历方法
let tree =  {
    id: '1',
    title: '节点1',
    children: [
      {
        id: '1-1',
        title: '节点1-1'
      },
      {
        id: '1-2',
        title: '节点1-2',
        children: [{
          id: '2',
          title: '节点2',
          children: [
            {
              id: '2-1',
              title: '节点2-1'
            }
          ]
        }]
      }
    ]
  }
  //主要级就是当前节点遍历完，然后再去遍历兄弟节点这样的顺序
let deepTraversal1 = (node, nodeList = []) => {
    if (node !== null) {
      nodeList.push(node.id)
      if(node.children && node.children.length>0){
        let children = node.children
        for (let i = 0; i < children.length; i++) {
          deepTraversal1(children[i], nodeList)
        }
      }
    }
    return nodeList
}
console.log(deepTraversal1(tree))