vue3常用的API使用简介

目录

• 生命周期的变更
• reactive
• ref
• 我们在vue2.x中获取元素标签是用 ref ，vue3.x我们要获取元素标签怎么办呢？
• toRef
• toRefs
• shallowReactive
• shallowRef
• toRaw
• markRaw
• watchEffect
• getCurrentInstance
• useStore

<template>
 <div id="app">
 <!-- 4. 访问响应式数据对象中的 count -->
 {{ state.count }}
 </div>
</template>
<script>
// 1. 从 vue 中导入 reactive 
import {reactive} from 'vue'
export default {
 name: 'App',
 setup() {
 // 2. 创建响应式的数据对象
 const state = reactive({count: 3})
 // 3. 将响应式数据对象state return 出去，供template使用
 return {state}
 }
}
</script>

<script>
import {ref, reactive} from 'vue'
export default {
 name: 'App',
 setup() {
 const obj = {count: 3}
 const state1 = ref(obj)
 const state2 = reactive(obj)
 console.log(state1)
 console.log(state2)
 }
}
</script>

<template>
 <div>
 <div ref="el">div元素</div>
 </div>
</template>
<script>
import { ref, onMounted } from 'vue'
export default {
 setup() {
 // 创建一个DOM引用，名称必须与元素的ref属性名相同
 const el = ref(null)
 // 在挂载后才能通过 el 获取到目标元素
 onMounted(() => {
  el.value.innerHTML = '内容被修改'
 })
 // 把创建的引用 return 出去
 return {el}
 }
}
</script>

<script>
// 1. 导入 toRef
import {toRef} from 'vue'
export default {
 setup() {
  const obj = {count: 3}
  // 2. 将 obj 对象中属性count的值转化为响应式数据
  const state = toRef(obj, 'count')
  // 3. 将toRef包装过的数据对象返回供template使用
  return {state}
 }
}
</script>

<template>
 <p>{{ state1 }}</p>
 <button @click="add1">增加</button>
 <p>{{ state2 }}</p>
 <button @click="add2">增加</button>
</template>
<script>
import {ref, toRef} from 'vue'
export default {
 setup() {
  const obj = {count: 3}
  const state1 = ref(obj.count)
  const state2 = toRef(obj, 'count')
  function add1() {
   state1.value ++
   console.log('原始值：', obj);
   console.log('响应式数据对象：', state1);
  }
  function add2() {
   state2.value ++
   console.log('原始值：', obj);
   console.log('响应式数据对象：', state2);
  }
  return {state1, state2, add1, add2}
 }
}
</script>

<script>
// 1. 导入 toRefs
import {toRefs} from 'vue'
export default {
 setup() {
  const obj = {
   name: '前端印象',
   age: 22,
   gender: 0
  }
  // 2. 将 obj 对象中属性count的值转化为响应式数据
  const state = toRefs(obj)
  // 3. 打印查看一下
  console.log(state)
 }
}
</script>

<script>
<template>
 <p>{{ state.a }}</p>
 <p>{{ state.first.b }}</p>
 <p>{{ state.first.second.c }}</p>
 <button @click="change1">改变1</button>
 <button @click="change2">改变2</button>
</template>
<script>
import {shallowReactive} from 'vue'
export default {
 setup() {
  const obj = {
   a: 1,
   first: {
   b: 2,
   second: {
    c: 3
   }
   }
  }
  const state = shallowReactive(obj)
  function change1() {
   state.a = 7
  }
  function change2() {
   state.first.b = 8
   state.first.second.c = 9
   console.log(state);
  }
  return {state}
 }
}
</script>

<template>
 <p>{{ state.a }}</p>
 <p>{{ state.first.b }}</p>
 <p>{{ state.first.second.c }}</p>
 <button @click="change">改变</button>
</template>
<script>
import {shallowRef, triggerRef} from 'vue'
export default {
 setup() {
  const obj = {
   a: 1,
   first: {
   b: 2,
   second: {
    c: 3
   }
   }
  }
  const state = shallowRef(obj)
  console.log(state);
  function change() {
   state.value.first.b = 8
   state.value.first.second.c = 9
   // 修改值后立即驱动视图更新
   triggerRef(state)
   console.log(state);
  }
  return {state, change}
 }
}
</script>

<script>
import {reactive, toRaw} from 'vue'
export default {
 setup() {
  const obj = {
   name: '前端印象',
   age: 22
  }
  const state = reactive(obj) 
  const raw = toRaw(state)
  console.log(obj === raw) // true
 }
}
</script>

<template>
 <p>{{ state.name }}</p>
 <p>{{ state.age }}</p>
 <button @click="change">改变</button>
</template>
<script>
import {reactive, markRaw} from 'vue'
export default {
 setup() {
  const obj = {
   name: '前端印象',
   age: 22
  }
  // 通过markRaw标记原始数据obj, 使其数据更新不再被追踪
  const raw = markRaw(obj) 
  // 试图用reactive包装raw, 使其变成响应式数据
  const state = reactive(raw) 
  function change() {
   state.age = 90
   console.log(state);
  }
  return {state, change}
 }
}
</script>

<script>
import {reactive, watchEffect} from 'vue'
export default {
 setup() { 
   const state = reactive({ count: 0, name: 'zs' })
   watchEffect(() => {
   console.log(state.count)
   console.log(state.name)
   /* 初始化时打印：
     0
     zs
   1秒后打印：
     1
     ls
   */
   })
   setTimeout(() => {
   state.count ++
   state.name = 'ls'
   }, 1000)
 }
}
</script>

<template>
 <p>{{ num }}</p>
</template>
<script>
import {ref, getCurrentInstance} from 'vue'
export default {
 setup() { 
  const num = ref(3)
  const instance = getCurrentInstance()
  console.log(instance)
  return {num}
 }
}
</script>

// store 文件夹下的 index.js
import Vuex from 'vuex'
const store = Vuex.createStore({
 state: {
  name: '前端印象',
  age: 22
 },
 mutations: {
  ……
 },
 ……
})
// example.vue
<script>
// 从 vuex 中导入 useStore 方法
import {useStore} from 'vuex'
export default {
 setup() { 
  // 获取 vuex 实例
  const store = useStore()
  console.log(store)
 }
}
</script>