Re:Engineering for Slow Internet
by arp242 on Friday May 31, 2024 @08:05PM
(#40541555)
There's quite some space between "100% no JS" and "full SPA"; many applications are mostly backend template-driven, but use JS async loads for some things where it makes sense. The vote buttons on Hacker News is a good example.
I agree a lot of full SPAs are poorly done, but some are do work well. FastMail is an example of a SPA done well.
The reason many SPAs are slower is just latency; traditional template-driven is:
- You send request
- Backend takes time to process that
- Sends all the data in one go.
- Browser renders it.
But full SPA is:
- You send request
- You get a stub template which loads JS.
- You load the JS.
- You parse the JS.
- You send some number of requests to get some JSON data, this can be anything from 1 to 10 depending on how it was written. Sometimes it's even serial (e.g. request 1 needs to complete, then uses some part of that to send request 2, and then that needs to finish).
- Your JS parses that and converts it to HTML.
- It injects that in your DOM.
- Browser renders it.
There are ways to make that faster, but many don't.
I agree a lot of full SPAs are poorly done, but some are do work well. FastMail is an example of a SPA done well.
The reason many SPAs are slower is just latency; traditional template-driven is:
- You send request
- Backend takes time to process that
- Sends all the data in one go.
- Browser renders it.
But full SPA is:
- You send request
- You get a stub template which loads JS.
- You load the JS.
- You parse the JS.
- You send some number of requests to get some JSON data, this can be anything from 1 to 10 depending on how it was written. Sometimes it's even serial (e.g. request 1 needs to complete, then uses some part of that to send request 2, and then that needs to finish).
- Your JS parses that and converts it to HTML.
- It injects that in your DOM.
- Browser renders it.
There are ways to make that faster, but many don't.