一、Promise.all

简述

Promise.all可以将多个Promise实例包装成一个新的Promise实例。同时，成功和失败的返回值是不同的，成功的时候返回的是一个结果数组，而失败的时候则返回最先被reject失败状态的值。Promse.all在处理多个异步处理时非常有用，比如说一个页面上需要等两个或多个ajax的数据回来以后才正常显示，在此之前只显示loading图标。
注意： Promise.all成功结果数组里的数据顺序和Promise.all接收到的数组顺序是一致的。 所以在前端开发请求数据的过程中，偶尔会遇到发送多个请求并根据请求顺序获取和使用数据的场景，使用Promise.all毫无疑问可以解决这个问题。

举例

let P1 = new Promise((resolve, reject) => {resolve('成功')
})let P2 = new Promise((resolve, reject) => {resolve('success')
})let P3 = Promse.reject('失败')Promise.all([P1, P2]).then((result) => {console.log(result)     //控制台打印结果['成功了', 'success']
}).catch((error) => {console.log(error)
})Promise.all([P1,P3,P2]).then((result) => {console.log(result)
}).catch((error) => {console.log(error)      // 控制台打印结果 '失败'
})

实战

这里实现的功能是调用后台接口返回数据实现全选反选

<template><div class="table-container-wapper" id="apps-permission" v-loading="isTableLoading"><div class="func-btn"><el-button @click="selectInvert" class="invert">反选</el-button><span class="cur">/</span><el-button @click="selectAll" class="allSelect">全选</el-button></div><div class="choose"><div v-for="(item, index) in form" :key="index" class="select-list"><el-checkbox  v-model="item.select">{{ item.serviceName }}</el-checkbox></div></div><div class="foot"><el-button class="cancel" size="small" @click="$router.back()">取 消</el-button><el-button type="success" size="small" @click="submit">确 定</el-button></div></div>
</template>

<script>import BaseMixin from "@/mixins/base";
import request from "@/utils/request";
import SETTING from "@/settings";export default {mixins: [BaseMixin],data() {return {clientId: this.$route.query.id,form: [],};},created() {this.isTableLoading = truePromise.all([this.getServiceInfo(),this.getList()]).then(([form, data]) => {let hasArr = data.map(item => item.serviceId)form.forEach(item => {if(hasArr.includes(item.id)) {item.select = true}else {item.select = false}})this.form = formthis.isTableLoading = false}, _ => { this.isTableLoading = false})},methods: {getServiceInfo() {return new Promise((resolve, reject) => {request({url: `${SETTING.IOT_APPLICATION}/serviceInfo`,params: {page: this.pagination.page - 1,size: 1000,},}).then((res) => {if (res.code=== "200") {resolve(res.data.content)}reject()},(_) => {reject()this.$message({type: "error",message: _.message || "查询列表失败",});});})  },getList() {return new Promise((resolve, reject) => {request({url: `${SETTING.IOT_APPLICATION}/sdkAppServiceRelation/curRights/${this.clientId}`,}).then((res) => {if (res[SETTING.IOT_THING_MODEL_STATES] === "200") {resolve(res.data)}reject()},(_) => {reject()this.$message({type: "error",message: _.message || "查询列表失败",});});})},//全选selectAll() {console.log(111)this.form.forEach((item) => {item.select = true;});},//反选selectInvert() {this.form.forEach((item) => {item.select = !item.select;});},//提交submit() {let ids = this.form.filter(item => item.select).map(item => item.id)request({url: `${SETTING.IOT_APPLICATION}/sdkAppServiceRelation/rights`,method: "post",data: {clientId: this.clientId,ids: ids}}).then((res) => {if (res[SETTING.IOT_THING_MODEL_STATES] === "200") {this.$message({type: "success",message: res.msg || res.message ||  "操作成功",});this.$router.back()}},(_) => {reject()this.$message({type: "error",message: _.message || "查询列表失败",});});},},
};
</script>

<style lang="scss" scope>
#apps-permission {max-width: 1000px;.func-btn {overflow: hidden;margin-top: 10px;.invert {border: 0px;padding: 0;float: right;font-size: 16px;}.cur {margin-left: 5px;margin-right: 5px;float: right;font-size: 16px;}.allSelect {border: 0px;padding: 0;float: right;font-size: 16px;}}.choose {display: flex;flex-wrap: wrap;.select-list{margin-bottom: 12px;width: 25%;}}.foot {display: flex;justify-content: flex-end;margin-top: 20px;}
}
</style>

扩展知识：Promise.race，哪个结果快就返回哪个