fix: Replace custom repeatString function with repeat()

[DreierF]

Marked version:

5.0.3

Description

While working on #2805 I noticed that there are a few repeatString functions that could trivially be replaced with String.proptotype.repeat(), which is already used in some other places in the code anyway.

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[UziTech]

Thanks for doing this!

[calculuschild]

Looks like the old function was there because at the time .repeat() wasn't standard JS. That function was taken from StackOverflow in a thread asking about the fastest method. Just out of curiosity, is there any benchmark comparing the speed of that approach vs the built-in function?

[DreierF]

I didn't perform any benchmark, but I would assume that the built-in functionality should be at least as fast as the custom implementation. Actually I would expect it to be faster as a lot of the string allocation+concatenation can be done in one go in the native implementation.

Update: Did a benchmark now out of curiosity. Result: It depends 😅 If you count the cost of creating the function it the old version is always slower than repeat() on my M1 Max (slower on mobile). If you don't it depends on the browser. It's faster in Safari and Firefox even if you don't count the function creation and a tiny bit slower in Chrome (not significantly 1%).

[styfle]

Great, thanks!

[davisjam]

Should be same-or-faster unless we're repeating really small strings, in which case the implementation shouldn't matter anyway. But it's nice to use the built-in language feature.

Do all marked-supported language runtimes now support repeat?

[styfle]

We don't have a list of supported runtimes outside of Node.js as far I know.

We support Node.js 18 and newer since Marked 5.0.0 (see #2767)