RegEx that will match the last occurrence of dot in a string

Question

I have a filename that can have multiple dots in it and could end with any extension:

tro.lo.lo.lo.lo.lo.png

I need to use a regex to repla

Answer 1

Just use special replacement pattern $1 in the replacement string:

console.log("tro.lo.lo.lo.lo.lo.png".replace(/\.([^.]+)$/, "@2x.$1"));
// "tro.lo.lo.lo.lo.lo@2x.png"