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An easier way of using polyfills

hacks.mozilla.org

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Re: An easier way of using polyfills

#11

Post by ben336 »

Drakim wrote: post #9
ben336 wrote: post #7

Earlier quoted context omitted.

You can't use feature detection with a simple script tag. It's calling in a script and the cdn chooses the file to send based on the user-agent. No Javascript is run that would allow it to feature detect before choosing to send the load. There may be feature detection afterwards of course.

While the roundabout trip would be a waste, it shouldn't be hard to just include a quick and simple feature detection before the polyfill is injected. I don't see any reason why one wouldn't do it.

Quick and simple meaning... are you checking for every feature back to ES3?

The point of this service is that its not requiring the user to know what feature to look for. They'll polyfill anything thats needed. To do feature detection to the level they're trying to serve you'd have to check EVERY API that needs polyfilled on an in-use browser. Full feature detection also involves looking for apis that exist but don't follow the spec. Checking every single API possible on every browser would not be quick and simple. User agents allow them to settle on a list of known needed polyfills without any code needed for the user beyond a simple script tag.

There are definitely tradeoffs to their approach but I can't say "I don't see any reason" why you wouldn't feature detect for this.

Re: An easier way of using polyfills

#12

Post by ben336 »

coldnebo wrote: post #10
ben336 wrote: post #7

Earlier quoted context omitted.

You can't use feature detection with a simple script tag. It's calling in a script and the cdn chooses the file to send based on the user-agent. No Javascript is run that would allow it to feature detect before choosing to send the load. There may be feature detection afterwards of course.

I think we're saying that most modern polyfills do a feature check before installing the polyfill... thus if you use Chrome with an IE agent, the polyfill still checks before implementing -- it's just a little slower than not installing the polyfill to begin with. Anyway, given the percentage of people who do this, UA detection seems like an acceptable tradeoff.

Agreed, feature detecting afterwards makes sense. Others seem to be suggesting feature detecting before requesting the polyfill script.

Re: An easier way of using polyfills

#13

Post by nostrademons »

AnkhMorporkian wrote: post #2

While a neat idea in theory, I have some qualms about this. User agent detection sounds great, until you have a user that spoofs their agent. I often do so for various reasons, and from time to time I forget to turn it off after I've finished what I was doing. If this service becomes common, then I will be given broken webpages seemingly at random. The other option, a polyfill covering specific features and served to…

That's a good reminder to turn off your user-agent spoofing. ;-)

Re: An easier way of using polyfills

#14

Post by watty »

AnkhMorporkian wrote: post #2

While a neat idea in theory, I have some qualms about this. User agent detection sounds great, until you have a user that spoofs their agent. I often do so for various reasons, and from time to time I forget to turn it off after I've finished what I was doing. If this service becomes common, then I will be given broken webpages seemingly at random. The other option, a polyfill covering specific features and served to…

And if you forget to turn Javascript back on things will break too.

Re: An easier way of using polyfills

#15

Post by logicallee »

AnkhMorporkian wrote: post #2

While a neat idea in theory, I have some qualms about this. User agent detection sounds great, until you have a user that spoofs their agent. I often do so for various reasons, and from time to time I forget to turn it off after I've finished what I was doing. If this service becomes common, then I will be given broken webpages seemingly at random. The other option, a polyfill covering specific features and served to…

Why do you think browsers report user agents? I think it's perfectly reasonable to serve the browser that you say you are.

If a lot of the pages you view end up broken, you would just change the way you lie about your user agent so that it's more prominent to you so you don't forget.

Your complaint is like complaining that if you set your browser's "language preference"* to only contain Dutch, you will end up getting served pages in Dutch.

Why is that different? You ask for Dutch only because supposedly you can understand it, and you ask for a presentation against a particular browser/version because supposedly you're rendering in it. Seems fine to me!

Otherwise, we might as well only serve pages in Esperanto - you know, the universal language standard.

* "(or, more appropriately, that of its user) along with every HTTP request being made in the form of the Accept-Language header that is part of the HTTP/1.1 RFC"

Re: An easier way of using polyfills

#19

Post by chc »

[deleted] wrote: post #16

[deleted]

I don't see what's stupid about that. Are you suggesting that anytime we want to talk about polyfills, we should instead write the following?

  #include "config.h"

  // ...

  #if !HAVE_FOOBAR
  void foobar(...)  // missing: implement ourselves
  {
  }
  #endif
Because that's nuts. This usage is actually more useful than the one that's a contraction of "polygon filling."
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