ES7异步 — Async/Await 文件读取下载

ES7异步 — Async/Await

纵观JS的异步操作Ajax、Promise，到如今ES7的Async/Await，前端Javascript朝着越来越规范化的方向前进着，嗯，废话说完了，来我们看例子吧

根据电影文件名，自动下载对应的海报，如下：

import fs from 'fs';
import path from 'path';
import request from 'request';

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)));
        });
    });
};

// 获取海报
var getPoster = function (movieName) {
    let url = `https://api.douban.com/v2/movie/search?q=${encodeURI(movieName)}`;

    return new Promise(function (resolve, reject) {
        request({url: url, json: true}, function (error, response, body) {
            if (error) return reject(error);

            resolve(body.subjects[0].images.large);
        })
    });
};

// 保存海报
var savePoster = function (movieName, url) {
    request.get(url).pipe(fs.createWriteStream(path.join(movieDir, movieName + '.jpg')));
};


(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 ===');
})();

此致那个敬礼！