Async file download in JavaScript and Python

https://github.com/begoon/tmpz/tree/main/async-download

Goals

1. Implement async file download in JavaScript and Python.
2. Compare the download speed.
3. Compare the order of downloads.
4. Compare the error handling.

Python

poetry install
poetry shell

python main.py

Python Results

downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
2: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
1: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
5: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
3: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
0: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
9: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
8: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
7: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
6: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
[[10485760, 0], [10485760, 1], [10485760, 2], [10485760, 3], Exception('random exception: n=4'), [10485760, 5], [10485760, 6], [10485760, 7], [10485760, 8], [10485760, 9]]
10 files downloaded in 23.77 seconds
throughput 3.79 MB/s

JavaScript

deno run -A main.js

or

bun main.js

JavaScript results

downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
downloading http://ipv4.download.thinkbroadband.com/10MB.zip
0: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
8: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
7: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
3: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
5: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
1: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
6: downloaded http://ipv4.download.thinkbroadband.com/10MB.zip, 10485760 bytes
[
  { status: "fulfilled", value: { n: 0, sz: 10485760 } },
  { status: "fulfilled", value: { n: 1, sz: 10485760 } },
  {
    status: "rejected",
    reason: Error: random error: n=2
    at download_file (file:///Users/...[reducted].../async-download/main.ts:9:36)
    at file:///Users/...[reducted].../async-download/main.ts:21:54
    at Array.map (<anonymous>)
    at main (file:///Users/...[reducted].../async-download/main.ts:21:40)
    at file:///Users/...[reducted].../async-download/main.ts:36:1
  },
  { status: "fulfilled", value: { n: 3, sz: 10485760 } },
  {
    status: "rejected",
    reason: Error: random error: n=4
    at download_file (file:///Users/...[reducted].../async-download/main.ts:9:36)
    at file:///Users/...[reducted].../async-download/main.ts:21:54
    at Array.map (<anonymous>)
    at main (file:///Users/...[reducted].../async-download/main.ts:21:40)
    at file:///Users/...[reducted].../async-download/main.ts:36:1
  },
  { status: "fulfilled", value: { n: 5, sz: 10485760 } },
  { status: "fulfilled", value: { n: 6, sz: 10485760 } },
  { status: "fulfilled", value: { n: 7, sz: 10485760 } },
  { status: "fulfilled", value: { n: 8, sz: 10485760 } },
  {
    status: "rejected",
    reason: Error: random error: n=9
    at download_file (file:///Users/...[reducted].../async-download/main.ts:9:36)
    at file:///Users/...[reducted].../async-download/main.ts:21:54
    at Array.map (<anonymous>)
    at main (file:///Users/...[reducted].../async-download/main.ts:21:40)
    at file:///Users/...[reducted].../async-download/main.ts:36:1
  }
]
10 files downloaded in 19 seconds
throughput: 3.78 MB/s

Conclusion

1. Both Python and JavaScript download speeds are about the same.
2. As a result, the order of resolved Promises in JavaScript and Async Tasks in Python is preserved.