Typescript: Use const enums where possible

[leeoniya]

What would you like to be added:

switch from using enum to const enum where possible:

https://www.typescriptlang.org/docs/handbook/enums.html#const-enums

Why is this needed:

there are currently 74 TypeScript enums in the Grafana codebase:

https://github.com/grafana/grafana/search?q=%22export+enum%22

each of these generates a JavaScript backing object that is then used to reference into. in the overwhelming majority of cases (where enums are static and do not need to be iterated), this is unecessary perf and byte overhead. the simple fix is to switch to using const enum, which compiles down to the final value. you can see the difference in the generated output by removing const from this demo:

https://www.typescriptlang.org/play?ts=4.0.5#code/KYDwDg9gTgLgBAYwgOwM72MgrgWzgMQgjgG8AoOSuADTgF44BWAGgqoE164A2VquAFpcA7KwC+ZMgBtg8EF0IQAdNQDcQA

[torkelo]

Should be possible for most enums, for some we do iterate over the keys

[leeoniya]

babel blocker: babel/babel#8741

[leeoniya]

possible unblocker: https://github.com/dosentmatter/babel-plugin-const-enum

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last year. It will be closed in 30 days if no further activity occurs. Please feel free to leave a comment if you believe the issue is still relevant. Thank you for your contributions!

[github-actions]

This issue has been automatically closed because it has not had any further activity in the last 30 days. Thank you for your contributions!