diff算法中的patch

1.初始化 patch(container,vnode)

2.更新 update(vnode,newVnode)

/*
 * @Autor: CQJ
 * @Date: 2022-05-23 16:57:11
 * @LastEditors: CQJ
 * @LastEditTime: 2022-05-23 17:18:55
 * @Description:
 */
function createElement(vnode) {
  //虚拟dom生成三要素
  let target = vnode.tag; //目标元素 ul
  let attrs = vnode.attrs || {}; //属性
  let children = vnode.children || []; //子元素
  if (!target) {
    return;
  }
  //1.创建对应dom
  let ele = document.createElement(target);
  let attrName = Object.keys(attrs);
  //2.给dom添加属性
  for (let i = 0; i < attrName.length; i++) {
    let attr = attrName[i];
    //class
    ele.setAttribute(attr, attrs[attr]);
  }
  //3.给dom添加子元素
  for (let i = 0; i < children.length; i++) {
    let child = children[i];
    //如果还有子元素，递归调用
    ele.appendChild(createElement(child));
  }
  return ele;
}
function updateChildren(vnode, newVnode) {
  let children = vnode.children || []; //现有节点
  let newChildren = newVnode.children || []; //新节点
  children.forEach((childrenVnode, index) => {
    //循环每一项
    let newChildrenvnode = newChildren[index];
    updateElement(childrenVnode, newChildrenvnode);
  });
}
function updateElement(vnode, newVnode) {
  if (!newVnode) return;
  if (!vnode) return;
  //如果第一层的标签tag不一样，那么就需要创建新的元素
  if (newVnode.tag !== vnode.tag) {
    replaceChildren(childrenVnode, newChildrenvnode);
  }
  //如果第一层的标签一样，那么就需要更新属性,深层次对比=>递归
  updateChildren(childrenVnode, newChildrenvnode);
}