It would be nice if it can resume from file 🙂

'MultipartDownload' class is inherited from and extends the 'EventEmitter' class, so it should emit 'error' events in case of app fail.
Try/catch statement in JS can't intercept async errors and throwing exceptions is pretty useless.
For example error in multipart-download.ts#L68 will never be handled, as network request was processed asynchronously, This one can be easily reproduced and tested if your dev server doesn't return 'accept-ranges' header.
I think it's good idea to swap all throw statements with this.emit('error', errMsg)...

Hello! I found your lib is very useful, but faced some little bugs.
First use callback form of calling writeStream.end() in ../src/models/multipart-download.d.ts (.js), it's reducing a lot errors caused by async behaviour when using this lib heavily.
So, instead emitting 'end' event right after, you should call this in end method callback:

new partial_download_1.default()
...
.on('end', () => {
  if (options.saveDirectory) {
    writeStream.end(() => {
      // do the job here
      if (++endCounter === options.numOfConnections) {
        this.emit('end', filePath);
      }
    });
  }
 });

I know, i should PR this, but i'm very lazy to mess with typescript, lol.

I'm using "multipart-download" in a complex scenario, where downloaded file should be streamed as http response and then removed (offtopic: it's would be great if this lib could expose option to write into Buffer, not only to filesystem), but there is problem - downloaded file can't be released and available for erasing only when node process shuts down.

Following sample of code shows that file can't be removed once it's have been completely downloaded, at least on Windows 10 x64 2015 LTSB.

const MultipartDownload = require('multipart-download')
const fs = require('graceful-fs')

const removeFile = filePath => {
  console.log('remove file called')
  fs.unlink(filePath, err => {
    if (err)
      return console.error(err)
  })
}

new MultipartDownload()
  .start('... any direct file url goes there ...', {
    numOfConnections: 5,
    saveDirectory: process.cwd(),
    fileName: 'file.bin'
  })
  .on('end', (filePath) => {
    console.log(`Downloaded file path: ${filePath}`)
    setTimeout(() => { /* just to keep node running for 1 min */ }, 60000)
    // Locked! File actually is only marked for removal, and will be really erased once node process stops
    setTimeout(() => removeFile(filePath), 100)
  })

Note that there is no difference between 'fs' and 'graceful-fs' modules (even if i replace all fs-require sections inside 'multipart-download' lib), problem still exists.
I'm solved this partially using 'cluster' module and running 'multipart-download' as a separate process.
Probably related to same problems in different modules: Multi-threaded-downloader #187 issue

Hello. How can I specify HTTP headers like Authorization in my request for accessing some restricted resources?

There is a certain probability of occurrence, the file size is correct, but MD5 is inconsistent.

When I downloaded a large file, I suddenly disconnected. Later, I executed the download. Is this library loaded or re-downloaded?

Thank you for your awesome package.

When i try to download a mp4 file, It had an error when try to send a HEAD request to url. Then app crashed.
The root cause is on
src/models/partial-request-query.ts#L22-L23

acceptRanges: res.headers['accept-ranges'],
contentLength: parseInt(res.headers['content-length'])

In this case, res is undefined.

Can you fix this?

It makes sense that if the user begins downloading a large file, he'll be able to cancel the download at any time.

nice work but missing support for reporting progress, please add it

Code example

const MultipartDownload = require('multipart-download');

const multipartDownload = (url) => {
  return new Promise((resolve, reject) => {
    new MultipartDownload()
      .start(url, {
        numOfConnections: 4,
        writeToBuffer: true,
      })
      .on('error', (err) => {
        console.log(err);
        reject(err);
      })
      .on('end', (buffer) => {
        console.log(buffer);
        resolve(buffer);
      });
  });
};

module.exports = multipartDownload;

It would be really great if you add a way to get total amount of data in order to calculate percent downloaded or download speed.
Thanks.

According to src/models/operation-factory.ts, options.headers will not be passed to request in any case.