<div id="app">
  <my-button></my-button>
</div>
<script>
 Vue.component("my-button", {
    template: "<button> 按鈕組件</button>",
   });
let vm = new Vue({
	el:'#app'
});
</script>

Vue.options._base = Vue; //可以通過(guò)\_base 找到 vue
Vue.options.components = {}; 

Vue.component = function (id, definition) {
  //每個(gè)組件產(chǎn)生一個(gè)新的類去繼承父親
  definition = this.options._base.extend(definition);

  console.log("1.給組件創(chuàng)造一個(gè)構(gòu)造函數(shù)，基于Vue", definition);

  this.options.components[id] = definition;
 };

import {mergeOptions} from '../util/index'
Vue.extend = function (definition) {
  const Vue = this;
  const Sub = function VueComponent(options) {
   this._init(options);
  };
  Sub.prototype = Object.create(Vue.prototype);
  Sub.prototype.constructor = Sub;
  Sub.options = mergeOptions(Vue.options, definition); 
  return Sub;
 };

strats.components = function (parentVal, childVal) {
 let options = Object.create(parentVal);
 if (childVal) {
  for (let key in childVal) {
   options[key] = childVal[key];
  }
 }
 return options;
};

 Vue.prototype._init = function (options) {
  const vm = this;
 ++ vm.$options = mergeOptions(vm.constructor.options, options); 
  //...
  initState(vm);
  if (vm.$options.el) {
   //將數(shù)據(jù)掛載到這個(gè)模版上
   vm.$mount(vm.$options.el);
  }
 };

export function isReservedTag(str) {
 let reservedTag = "a,div,span,p,img,button,ul,li";
 return reservedTag.includes(str);
}

export function createElement(vm, tag, data = {}, ...children) {
  // 如果tag是組件 應(yīng)該渲染一個(gè)組件的vnode
  if (isReservedTag(tag)) {
    return vnode(vm, tag, data, data.key, children, undefined);
  } else {
    const Ctor = vm.$options.components[tag]
    return createComponent(vm, tag, data, data.key, children, Ctor);
  }
}
// 創(chuàng)建組件的虛擬節(jié)點(diǎn), 為了區(qū)分組件和元素 data.hook 
function createComponent(vm, tag, data, key, children, Ctor) {
  // 組件的構(gòu)造函數(shù)
  if(isObject(Ctor)){
    Ctor = vm.$options._base.extend(Ctor); // Vue.extend 
  }
  data.hook = { // 等會(huì)渲染組件時(shí) 需要調(diào)用此初始化方法
    init(vnode){
      let vm = vnode.componentInstance = new Ctor({_isComponent:true}); // new Sub 會(huì)用此選項(xiàng)和組件的配置進(jìn)行合并
      vm.$mount(); // 組件掛載完成后 會(huì)在 vnode.componentInstance.$el 
    }
  }
  return vnode(vm,`vue-component-${tag}`,data,key,undefined,undefined,{Ctor,children})
}

export function patch(oldVnode,vnode){
  // 1.判斷是更新還是要渲染
  if(!oldVnode){
    return createElm(vnode);
  }else{
    // ...
  }
}

function createElm(vnode) {
 let { tag, data, children, text, vm } = vnode;
 if (typeof tag === "string") {
  if (createComponent(vnode)) {
   //返回組件對(duì)應(yīng)的真實(shí)節(jié)點(diǎn)
   return vnode.componentInstance.$el;
  }
  vnode.el = document.createElement(tag); // 虛擬節(jié)點(diǎn)會(huì)有一個(gè)el屬性,對(duì)應(yīng)真實(shí)節(jié)點(diǎn)
  children.forEach((child) => {
   vnode.el.appendChild(createElm(child));
  });
 } else {
  vnode.el = document.createTextNode(text);
 }
 return vnode.el;
}

function createComponent(vnode) {
  let i = vnode.data;
  if((i = i.hook) && (i = i.init)){
    i(vnode);
  }
  if(vnode.componentInstance){
    return true;
  }
}

data.hook = {
  init(vnode){
    let child = vnode.componentInstance = new Ctor({});
    child.$mount(); // 組件的掛載
  }
}