Using template strings as progress bars

progress.js

"use strict"

function progress(strs, current, total) {
  let str = `${strs[0]}${current}${strs[1]}${total}${strs[2]}`
  let ratio = Math.min(Math.max(current / total, 0), 1)
  let length = Math.floor(ratio * str.length)
  let pattern = new RegExp(`^.{${length}}`)

  return str.replace(pattern, "\x1b[4m$&\x1b[0m")
}

void function loop(current, total) {
  let message = progress`${current} of ${total} pages crawled`

  process.stderr.write(`  ${message}`)
  process.stderr.clearLine(1)

  if (current == total) return process.stderr.write(": done.\n\n")

  process.stderr.cursorTo(0)

  let interval = 0 | Math.random() * 50

  setTimeout(loop, interval, ++current, total)
}(0, 200)