将缓冲区从ReadStream更改为实际文件

Question

所以我有这段代码：

downloadFile(file_id) {
    return new Promise((resolve, reject) => {
        var mongoose = require('mongoose');
        var Grid = require('gridfs-stream');
        var fs = require('fs');

        mongoose.connect(config.db, {useNewUrlParser: true},).catch(e => console.log(e));
        var conn = mongoose.connection;
        Grid.mongo = mongoose.mongo;
        var gfs = Grid(conn.db);
        console.log('downloadfile', file_id);
        var read_stream = gfs.createReadStream({_id: file_id});
        let file = [];
        read_stream.on('data', function (chunk) {
            file.push(chunk);
        });
        read_stream.on('error', e => {
            console.log(e);
            reject(e);
        });
        return read_stream.on('end', function () {
            resolve(file);
        });
    });
}

我这样称呼它：

Account.findById(req.params._id)
    .then(async account => {
        const file = await functions.downloadFile(account.employer.logo);
        res.render('users/employer/booth', {
            title: 'Employer Booth',
            user: req.user,
            postings: postings,
            employer: account.employer,
            event: event,
            logo: logo,
        });
    });

如何将该文件保存到服务器并用作图像，或者仅将其发送到视图并在<img>标签中显示？

我试图做这样的事情：

read_stream.on('open', function () {
    var imgFile = fs.createWriteStream(`/public/images/logos/${file_id}.jpg`);
    var write_stream = read_stream.pipe(imgFile);
    read_stream.pipe(res);
});
read_stream.on('error', e => {
    console.log(e);
});

但这无法读取已保存的文件，并且文件也未保存在任何地方。

Answer 1

好的，这挽救了我的生命：https :
//youtu.be/pXHOF4GWuZQ。这是最终代码：

downloadFile(file_id) {
    return new Promise((resolve, reject) => {
        var mongoose = require('mongoose');
        var Grid = require('gridfs-stream');
        var fs = require('fs');

        mongoose.connect(config.db, {useNewUrlParser: true},).catch(e => console.log(e));
        var conn = mongoose.connection;
        Grid.mongo = mongoose.mongo;
        var gfs = Grid(conn.db);
        console.log('downloadfile', file_id);
        var read_stream = gfs.createReadStream({_id: file_id});
        let file = [];
        read_stream.on('data', function (chunk) {
            file.push(chunk);
        });
        read_stream.on('error', e => {
            console.log(e);
            reject(e);
        });
        return read_stream.on('end', function () {
            file = Buffer.concat(file);
            const img = `data:image/png;base64,${Buffer(file).toString('base64')}`;
            resolve(img);
        });
    });
}