I'm going to keep this issue open for a while, just until the repo has settled a bit. Any performance-related improvements, pop a comment down below and I will add them to this list.

Current areas for improvement:

• Multiple for loops (resolved in #11)
• Multiple ifs (some nested unnecessarily) (resolved in #11)
• console.log alternative? Stripped most out of them from the primary scripts (non-min and min) - only concern here is impact to mobile devices. No "data" is being shared at all! (resolved in #11)
• A fair bit of repeated code in the loadMyScript function - move into helper functions? (resolved in #11)
• Repeated code in init function (resolved in #11)
• Always having to loop back to "core" function - can we just go step by step? (resolved in #11)
• Large number of "filler" variables (resolved in #11)
• Appending script to body - is the current method the best method for all devices (not just desktop, but mobile too)? (https://jsperf.com/create-element-direct-append-vs-get-elements/1)
• Variables: var, let or const?
• if's - are they being handled in the best way in general? switch/case or continue with if else (https://jsperf.com/switch-case-vs-if-else/13)
  • Windows 10, Chrome 71: if else = slowest vs object = fastst (switch-case close second)
• There's a set of nested ifs within the checking function. See https://github.com/willstocks-tech/dynamically-polyfill-features-for-a-script/blob/develop/dynamicpolyfill.js#L40+L46
• Complete some benchmarking on each function (and the script overall) just to see if there are any leaks/bottlenecks (see #12 (comment))
• dynamicPolyfill has become potentially "Cognitively Complex" (see: https://codeclimate.com/github/willstocks-tech/dynamically-polyfill-features-for-a-script/pull/19)

I am using the following branch

• master
• develop

Does this enhancement relate to an existing pull request

• Yes
• No
  If yes, PR: #

Describe the enhancement you'd like to see implemented

Resolve issues relating to cognitive complexity. See https://codeclimate.com/github/willstocks-tech/dynamically-polyfill-features-for-a-script/issues?category=complexity&engine_name%5B%5D=structure&engine_name%5B%5D=duplication

What are the benefits of implementation?

Code readability/supportability and overall complexity.

If applicable, describe any alternative solutions you've considered

Additional context

See: https://codeclimate.com/github/willstocks-tech/dynamically-polyfill-features-for-a-script/issues?category=complexity&engine_name%5B%5D=structure&engine_name%5B%5D=duplication - only file we're concerned about is the "core" dynamicpolyfill.js file - ignore any errors relating to -withinlinecomments.js

Have you worked on this yourself already? If so, link to your PR.

Changing from if() to if(!) would mean that the else can be removed from the sequence - removing unnecessary console.log. Overall code would be a little cleaner to look at/support

Branch being used

• master
• develop

Describe the issue

Individual requests are being made to polyfill.io, instead of all features being bundled into a single request

Troubleshooting steps taken

To Reproduce
Steps to reproduce the behavior:

1. Run script with all native features
2. Monitor network waterfall
3. See polyfill.io being called 3 times, when ['IntersectionObserver', 'IntersectionObserverEntry', 'Testing'] is being passed as the first parameter

Expected behavior

Only one request should be made to polyfill.io, with all features within that single request.

Screenshots

Desktop (please complete the following information):

• OS:
• Browser:
• Version:

Smartphone (please complete the following information):

• Device:
• Mobile OS:
• Browser:
• Version:

Additional Information
Add any other context about the problem here.

Some people (sensible people) might want to load an array of external scripts. Rather than request the polyfill features separately (resulting in multiple requests), allow the passing of the array of polyfill features (already exists) PLUS an array of scripts so that all polyfills can be requested at once, rather than all separately

Noticed this as Object.assign was being polyfilled in Chrome despite it having native support.

Branch being used

• master
• develop

Describe the issue

As of v0.0.5 polyfill.io is still being called, even when there's nothing to polyfill

Troubleshooting steps taken

To Reproduce
Steps to reproduce the behavior:

1. Run script with all native features
2. Monitor network waterfall
3. See polyfill.io being called with no features requested

Expected behavior

Don't call polyfill.io if we don't need to - the whole point of this is to not waste requests

Screenshots

N/A

Desktop (please complete the following information):

• OS: Windows 10, macOS
• Browser: Chrome, Safari
• Version: v72, latest stable macOS Safari

Smartphone (please complete the following information):

• Device:
• Mobile OS:
• Browser:
• Version:

Additional Information

Branch being used

• master
• develop

Describe the issue

Using .min.js results in a fair few errors + the script not actually executing (and potentially breaking other scripts on a site!)

Troubleshooting steps taken

Using non-minified, everything works fine. It looks like the uglification process changes things so much that things just aren't happy!
Trying to minify using different methods.

To Reproduce
Steps to reproduce the behavior:

1. Copy the min.js file
2. Paste it into a project/page
3. Save and then reload a page that was known to work
4. View console, see errors

Expected behavior

Shouldn't break anything. Should run in exactly the same manner as the non-minified version!

Screenshots

Desktop (please complete the following information):

• OS:
• Browser:
• Version:

Smartphone (please complete the following information):

• Device:
• Mobile OS:
• Browser:
• Version:

Additional Information
Add any other context about the problem here.

For some reason, in Chrome, init functions aren't executing. The code is validating and the function is parsing, but the actual function never executes...

Something to do with:

try {
	window[fn]
}

Which was implemented due to Safari being weird with new Function

Converting back to:

try {
	var run = new Function(fn);
	run();
}

and stuff works.

Two options here...:

1. Make window[fn] work some how
2. Implement both methods in the same try... which feels wrong!

I refuse to use eval() based on SO/Google/very widespread opinion!

Also allow array of "initialisation" functions!

Originally posted by @willstocks-tech in #8 (comment)

Extend native support for features within checking(check)

Potentially related to #23

v0.0.5-beta.6

Safari (non-mobile) throws a bunch of weird errors on first load, then works perfectly fine on consecutive load.

Assumption: something to do with Promises

Polyfill promises before polyfilling the polyfills?

POLYFILL-CEPTION.

The polyfills we need to load are currently based on promises, which has fairly wide support (https://caniuse.com/#search=promise), except for IE11 and older versions of IE. Chances are, these are the browsers we'll want to be polyfilling functionality for, but can't because promises aren't supported.

Find a way to polyfill promises before running everything else... and without promise.then()

Rather than statically declaring variables, what about passing them through as a function. That way this little script could be loaded off a CDN and variables passed through to it? Would also allow "per page polyfilling" to work a lot easier, with a lot less maintenance?

checkPolyfills( [featuresArray], scriptURL ) or something like that?

I am using the following branch

• master
• develop

Does this enhancement relate to an existing pull request

• Yes
• No

If yes, note PR number here: #19

Describe the enhancement you'd like to see implemented

Add a version of the script with inline comments.

What are the benefits of implementation?

New users/contributors will be able to better understand what each step of the script is doing and why.

If applicable, describe any alternative solutions you've considered

N/A

Additional context

N/A

Have you worked on this yourself already? If so, link to your PR.

#19
See: dynamicpolyfill-withinlinecomments.js