vue3.0 上手体验

npm install -g @vue/cli

npm update -g @vue/cli

vue -V
@vue/cli 4.4.1

vue create vue3-demo

Vue CLI v4.4.1
? Please pick a preset:
  常用配置 (router, vuex, sass, babel, eslint)
  sass (router, vuex, sass, babel, eslint)
  test (less, babel, eslint)
  default (babel, eslint)
❯ Manually select features

Vue CLI v4.4.1
? Please pick a preset: Manually select features
? Check the features needed for your project:
 ◉ Babel
 ◯ TypeScript
 ◯ Progressive Web App (PWA) Support
 ◉ Router
 ◉ Vuex
❯◉ CSS Pre-processors
 ◉ Linter / Formatter
 ◯ Unit Testing
 ◯ E2E Testing

cd vue3-demo
vue add vue-next

import { createApp } from 'vue'
import App from './App.vue'
import router from './router'
import store from './store'

createApp(App).use(router).use(store).mount('#app')

// Vue2 创建实例

import Vue from 'vue'
import App from './App'
import router from './router'
import store from './store'

new Vue({
  el: '#app',
  router,
  store,
  render: h => h(App)
})

import { createRouter, createWebHistory } from 'vue-router'
import Home from '../views/Home.vue'

const routes = [
  {
    path: '/',
    name: 'Home',
    component: Home
  },
  {
    path: '/about',
    name: 'About',
    // route level code-splitting
    // this generates a separate chunk (about.[hash].js) for this route
    // which is lazy-loaded when the route is visited.
    component: () => import(/* webpackChunkName: "about" */ '../views/About.vue')
  }
]

const router = createRouter({
  history: createWebHistory(process.env.BASE_URL),
  routes
})

export default router

// Vue2
export default {
  // ....
  data() {
    return {
      state: {
        count: 0
      }
    };
  },
}

// Vue3
import { ref } from 'vue'
export default {
  setup () {
    const count = ref(0) // 声明 count，初始值为 0
    const str = ref('hello') // 声明 str，初始值为 'hello'
    return {
      count,
      str
    }
  }
}

<template>
  <div class="home">
   <p>count: {{count}}</p>
   <p>doubleCount: {{doubleCount}}</p>
   <button @click="add">增加</button>
  </div>
</template>

<script>
import { ref, watch, computed } from 'vue'
export default {
  setup () {
    // 声明 count 变量，初始值为 0
    const count = ref(0)

    // 定义 add 方法
    const add = () => {
      count.value++
    }

    // 定义 watch，需要手动引入 watch 方法
    watch(
      () => count.value,
      (val, oldVal) => { console.log(`new count: ${val}，old count: ${oldVal}`) }
    )

    // 定义computed，同样需要手动引入 computed 方法
    const doubleCount = computed(() => count.value * 2)

    return {
      count,
      add,
      doubleCount
    }
  }
}
</script>

<template>
  <div class="home">
    <p>str: {{state.str}}</p>
   <p>count: {{state.count}}</p>
   <button @click="add">增加</button>
  </div>
</template>

<script>
import { reactive } from 'vue'
export default {
  setup () {
    // 引入 reactive，同时定义多个变量
    const state = reactive({
      count: 0,
      str: 'hello'
    })

    // 现在访问变量，不能使用 .value 方式访问了
    const add = () => {
      // state.count.value++ // 错误
      state.count.value++
    }

    return {
      state,
      add
    }
  }
}
</script>

<script>
import { getCurrentInstance } from 'vue'
export default {
  setup () {
    const { ctx } = getCurrentInstance()
    console.log(ctx.$router.currentRoute.value)
  }
}
</script>

import Vuex from 'vuex'

export default Vuex.createStore({
  state: {
  },
  mutations: {
  },
  actions: {
  },
  modules: {
  }
})

// Vue2 中创建 store 实例
export default new Vuex.Store({
   // ... 
})

import Vuex from 'vuex'

export default Vuex.createStore({
  state: {
    count: 0
  },
  mutations: {
    ADD (state) {
      state.count++
    }
  },
  actions: {
    add ({ commit }) {
      commit('ADD')
    }
  },
  modules: {
  }
})

<template>
  <div class="home">
    <p>{{count}}</p>
    <button @click="add">增加</button>
  </div>
</template>

<script>
import { computed } from 'vue'
import { useStore } from 'vuex'
export default {
  setup () {
    const store = useStore()
    const count = computed(() => store.state.count)

    const add = () => {
      store.dispatch('add')
    }

    return {
      count,
      add
    }
  }
}
</script>

import {getCurrentInstance} from 'vue'

// ...
const store = getCurrentInstance().ctx.$store