>>623 javascript(es2018 named capture groups)
`
[sec1]
key1=val1

[sec2]
key2=val2
`.replace(/\[(?<section>.+)\]\n(?<key>.+)=(?<value>.+)\n/g, '$<section>:$<key>:$<value>').trim();
結果:
sec1:key1:val1
sec2:key2:val2