perf: only create regex once

[gtm-nayan]

With chalk/wrap-ansi#51, a large portion of the time in wrap-ansi is now spent in ansiRegex because strip-ansi creates a new regex on every call and it's called for every word in wrap-ansi.

Before:

After:

[sindresorhus]

You need to reset the .lastIndex and also benchmark with that to ensure it improves performance still.

[gtm-nayan]

Huh, weird, resetting the last index does actually make this function 2x slower, still a lot faster than before tho.

Good news is, I think the lastIndex doesn't have to be reset when using replace particularly, it does it automatically

[sindresorhus]

That is quite subtle. Found some info about it:

Because @@replace would keep calling exec() until it returns null, and exec() would automatically reset the regex's lastIndex to 0 when the last match fails, @@replace would typically not have side effects when it exits. However, when the regex is sticky but not global, lastIndex would not be reset. In this case, each call to replace() may return a different result.

[sindresorhus]

Can you add a short code comment that states why we don't need to reset .lastIndex. Otherwise, I fear it will be added in the future accidentally.