How to pad out line to certain length using regex replace and snippets

Question

// My Section -----------------------------------------------------------------

The above is the desired result.

---

Imagine this scenario

Answer 1

You can use callback function of replace and based on length you can replace values

let str = `// ----------------------------------------------------------------------------
// firebase

// ----------------------------------------------------------------------------
// utils`

let final = str.replace(/^.*$/gm, (match)=>{
  return match.length === 0 ? match : match.length > 20 ? match.substr(0,20) : match + `-`.repeat(20-match.length)
})

console.log(final)