Encountered undefined value during string replacement and weird behaviour

I have this string:
`let text = "{form 1} {form 2} {form 1:3}";`

and this regexp:
`/{form (\d+(:\d+)?)}/g`
that should match {form x} and {form x:y}

I am executing:

``text = reactStringReplace(text, /{form (\d+(:\d+)?)}/g, (match, i) => {
return 'match: ${match}, i: ${i}';
});``

then in the return of my component I have this:
```
return (

and this is de output:

```

As you can see, the first and third `

` are fine. But the rest aren`t.
The second is the matched value of {form 2} but didn't enter in the replace function.
The forth is only part of the matched value of {form 1:3} and also didn't enter in the function.
And the last did enters in the replace function but the match is "";