JavaScript implements depth-first traversal and breadth-first traversal of the DOM tree (code example)

What this article brings to you is about implementing depth-first traversal and breadth-first traversal of the DOM tree in JavaScript (code examples). It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Depth-first traversal

// 非递归,首次传入的node值为DOM树中的根元素点，即html
// 调用：deep(document.documentElement)
function deep (node) {
  var res = []; // 存储访问过的节点
  if (node != null) {
    var nodeList = []; // 存储需要被访问的节点
    nodeList.push(node);
    while (nodeList.length > 0) {
      var currentNode = nodeList.pop(); // 当前正在被访问的节点
      res.push(currentNode);
      var childrens = currentNode.children;
      for (var i = childrens.length - 1; i >= 0; i--) {
        nodeList.push(childrens[i]);
      }
    }
  }
  return res;
}

// 使用递归
var res = []; // 存储已经访问过的节点
function deep (node) {
  if (node != null) { // 该节点存在
    res.push(node);
    // 使用childrens变量存储node.children，提升性能，不使用node.children.length，从而不必在for循环遍历时每次都去获取子元素
    for (var i = 0,  childrens = node.children; i < childrens.length; i++) {
      deep(childrens[i]);
    }
  }
  return res;
}

Breadth-first traversal

// 递归
var res = [];
function wide (node) {
  if (res.indexOf(node) === -1) {
    res.push(node); // 存入根节点
  }
  var childrens = node.children;
  for (var i = 0; i < childrens.length; i++) {
    if (childrens[i] != null) {
      res.push(childrens[i]); // 存入当前节点的所有子元素
    }
  }
  for (var j = 0; j < childrens.length; j++) {
    wide(childrens[j]); // 对每个子元素递归
  }
  return res;
}

// 非递归
function wide (node) {
  var res = [];
  var nodeList = []; // 存储需要被访问的节点
  nodeList.push(node);
  while (nodeList.length > 0) {
    var currentNode = nodeList.shift(0);
    res.push(currentNode);
    for (var i = 0, childrens = currentNode.children; i < childrens.length; i++) {
      nodeList.push(childrens[i]);
    }   
  }
  return res;
}

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