node 开发中常用的async/await 处理回调的几种形式

来源：互联网发布：rem换算px 移动端js 编辑：程序博客网时间：2024/05/30 04:59

一、单一的回调处理

//下面两种形式的async函数效果相同，await只能用在async函数内部async function(){}async () => {}

（1）http请求

var http = require('http');(async () => {    var res = await new Promise(function (resolve, reject) {        var options = {            hostname: 'XXX.com',            path: "/api",            method: 'GET'        };        var req = http.request(options, function (res) {            console.log('STATUS: ' + res.statusCode);            console.log('HEADERS: ' + JSON.stringify(res.headers));            res.setEncoding('utf8');            res.on('data', function (chunk) {                console.log('BODY: ' + chunk);                resolve(chunk);            });        });        req.on('error', function (e) {            console.log('problem with request: ' + e.message);            reject(new Error('http failed'));        });        req.end();    });    console.log('request body:' + res);})();

（2）数据库查询

这里用sequelize作为orm中间件，配置好数据库连接后在函数内：

(async () => {    var Pets = await Pet.findAll({        offset: 0,        limit: 5,        where: {            id: 1                }    });       console.log(Pets[0].name); })();

（3）文件i/o

import fs from 'fs';import path from 'path';var movieDir = __dirname + '/movies',    exts     = ['.mkv', '.avi', '.mp4', '.rm', '.rmvb', '.wmv'];// 读取文件列表var readFiles = function () {    return new Promise(function (resolve, reject) {        fs.readdir(movieDir, function (err, files) {            resolve(files.filter((v) => exts.includes(path.parse(v).ext)));        });    });};(async () => {    let files = await readFiles();    // await只能使用在原生语法    for (var file of files) {        let name = path.parse(file).name;        console.log(`正在获取【${name}】的海报`);        savePoster(name, await getPoster(name));    }    console.log('=== 获取海报完成 ===');})();

二、多个并发的回调处理

比如服务器端多个请求可以并发运行，但需要都返回结果后再运行下面的代码，此处也可以是数据库，或者其他耗时回调操作，这里拿数据库操作举例

(async () => {    var petPromise = new Promise(function (resolve, reject) {        Pet.findOne({            where: {                id: 1            }        }).then(function (p) {            resolve(p);        }).catch(function (err) {            reject(new Error('failed: ' + err));        });    });    var perPromise = new Promise(function (resolve, reject) {        Pet.findOne({            where: {                id: 1            }        }).then(function (p) {            resolve(p);        }).catch(function (err) {            reject(new Error('failed: ' + err));        });    });    var argList = await Promise.all([petPromise, perPromise]);    console.log(argList[1].name + 'love' + argList[0].name)})();})();

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