Helpful. Thank you!

Thanks.

I, too, wondered what the empty array was for. Thanks for you explanation @Balkoth!

@bigtallbill Thanks for the link of MDN ^_^

very helpful, thanks

That makes sense. Thanks for the explaination @Balkoth.

I know it, but I forgot ! Sorry about that.

@Balkoth: Beware! Comments on kata solutions can be read even by those who haven't solved the kata yet. Don't forget to mark your comment as spoiler if it contains information related to the solution.

I think there’s absolutely no need to depend on such micro-benchmarks. The real bottlenecks are somewhere else. However, each of these conversion methods has its own caveats:

• v.toString() — works well, unless v.toString is not a function, that is when v is null or undefined or when .toString was deliberately changed or deleted (very rare case)
• '' + v — works with nulls and undefineds too, but might give some unexpected results for such objects as:

v = {
  valueOf: function () { return 5 },
  toString: function () { return 'foo' }
}

in which case '' + v would return '5' (very rare case)

• String(v) — works every time, correctly calls .toString method, if an object has one, and works for nulls and undefineds
• '' + [v] or [v].join() — same as String(v) (unless you modified Array.prototype), with exception of nulls and undefineds becoming empty strings, which can be quite usefull sometimes

In the real world, it’s fine to use any of these methods, with caution while using v.toString() when v could be null and undefined. Choose, what’s most convenient/legible/usefull for you and your team. Performance differences are highly negligible.