Bug: Template literals break older browsers

[jginsburgn]

Either:

1. (Better) Include transpilation for older JavaScript compatibility during buildtime of static assets.
2. (Good, and best if combined with 1) Set up testing with IE.
3. (Easy) Remove uses of template literals where they have been introduced (see below) and include rules for disallowing them.

Current occurrences of template literals (upon superficial skimming):

1. karma/client/updater.js

   Line 32 in e246461

   titleElement.textContent = `Karma v ${VERSION} - ${connectionText}; test: ${testText}; ${pingText}`

2. karma/client/updater.js

   Line 56 in e246461

   updateConnectionStatus(`reconnecting in ${sec} seconds`)

3. karma/client/updater.js

   Line 74 in e246461

   updatePingStatus(`ping ${latency}ms`)

4. karma/client/karma.js

   Line 194 in e246461

   self.updater.updateTestStatus(`karma_error ${message}`)

@johnjbarton awaiting your feedback on this...

[jginsburgn]

Ditto for arrow functions and their implications (i.e. use of this and others).

[devoto13]

See #3629 for (3).

[jginsburgn]

@devoto13 what do you think of the other options ((1) and (2))?

[devoto13]

I think (2) is a must to prevent such regressions in the future.

Re (1) I'm a bit on the fence. On one hand, it would be nice to write modern client JS and let tooling downlevel it to work in all browsers. We also already have a build process for client JS, so extending it with more capabilities wouldn't really change a workflow. On the other hand, it means more build tools to keep track of and maintain. In the past @johnjbarton didn't want to introduce more build tools to the repository, so I will let him decide.

[johnjbarton]

(2) is essential, but I can't get either browserstack or saucelabs to work in the time I had available.
(1) I think we should migrate the source to TypeScript and we could start with client/*. It brings a lot more tooling and issues but the benefits are also much larger and the tool support unequalled.
(3) I sent #3632 for the ugly option.

[devoto13]

@johnjbarton I can spend some time on debugging the cross-browser testing later this week if you grant access to BrowserStack / SauceLabs to devoto13 at gmail.com. So I can access their web apps and see what happens inside a VM.

[karmarunnerbot]

🎉 This issue has been resolved in version 6.0.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀