javascript - Node.js中如何一一下载文件？

Question

我正在尝试使用请求库下载多个文件，我需要将它们一一下载并显示进度条，文件链接存储在一个数组中，该数组将它们传递给一个函数以开始下载

const request = require('request')
const fs = require('fs')
const ProgressBar = require('progress')

async function downloadFiles(links) {
    for (let link of links) {
        let file = request(link)
        file.on('response', (res) => {
            var len = parseInt(res.headers['content-length'], 10);
            console.log();
            bar = new ProgressBar('  Downloading [:bar] :rate/bps :percent :etas', {
                complete: '=',
                incomplete: ' ',
                width: 20,
                total: len
            });
            file.on('data', (chunk) => {
                bar.tick(chunk.length);
            })
            file.on('end', () => {
                console.log('\n');
            })
        })
        file.pipe(fs.createWriteStream('./downloads/' + Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15)))
    }
}


let links = ['https://speed.hetzner.de/100MB.bin', 'https://speed.hetzner.de/100MB.bin', 'https://speed.hetzner.de/100MB.bin', 'https://speed.hetzner.de/100MB.bin']
downloadFiles(links)

这就是我到目前为止所得到的，问题是请求是异步的，我尝试使用 async/await 但这样我无法让进度条工作。如何才能让文件一次下载一个，并且还有进度条呢？

Answer 1

基于我对 async.queue 的评论，这就是我要写的方式。您可以调用dl.downloadFiles([])只要您想要，它就会依次获取您添加到队列中的所有内容。

const request = require('request')
const async = require('async')
const fs = require('fs')
const ProgressBar = require('progress')

class Downloader {
    constructor() {
        this.q = async.queue(this.singleFile, 1);

        // assign a callback
        this.q.drain(function() {
            console.log('all items have been processed');
        });

        // assign an error callback
        this.q.error(function(err, task) {
            console.error('task experienced an error', task);
        });
    }

    downloadFiles(links) {
        for (let link of links) {
            this.q.push(link);
        }
    }

    singleFile(link, cb) {
        let file = request(link);
        let bar;
        file.on('response', (res) => {
            const len = parseInt(res.headers['content-length'], 10);
            console.log();
            bar = new ProgressBar('  Downloading [:bar] :rate/bps :percent :etas', {
                complete: '=',
                incomplete: ' ',
                width: 20,
                total: len
            });
            file.on('data', (chunk) => {
                bar.tick(chunk.length);
            })
            file.on('end', () => {
                console.log('\n');
                cb();
            })
        })
        file.pipe(fs.createWriteStream('./downloads/' + Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15)))
    }
}

const dl = new Downloader();

dl.downloadFiles([
    'https://speed.hetzner.de/100MB.bin',
    'https://speed.hetzner.de/100MB.bin'
]);