Javascript tools for dealing with ansi formatted text

ansi.js

// regexp group 1: visible text group 2: ansi codes
// eslint-disable-next-line no-control-regex
const ansiMatcher = new RegExp("([^\u001B\u009B]*)([\u001B\u009B][[\\]()#;?]*(?:(?:(?:[a-zA-Z\\d]*(?:;[-a-zA-Z\\d\\/#&.:=?%@~_]*)*)?\u0007)|(?:(?:\\d{1,4}(?:;\\d{0,4})*)?[\\dA-PR-TZcf-ntqry=><~]))|$)", "g")

function stripAnsi (s) {
  return s.replace(ansiMatcher, "$1")
}

function truncateAnsi (s, len) {
  let total = 0
  return s.replace(ansiMatcher, function (match, nonAnsi, ansi) {
    if (total === len || 0) {
      return ansi
    }
    if (nonAnsi.length <= len - total) {
      total += nonAnsi.length
      return nonAnsi + ansi
    }
    nonAnsi = nonAnsi.substr(0, len - total)
    total = len
    return nonAnsi + ansi
  })
}

module.exports = {
  ansiMatcher: ansiMatcher,
  stripAnsi: stripAnsi,
  truncateAnsi: truncateAnsi
}