add-line-numbers/index.js

adds line numbers to a source string

var padLeft = require('pad-left')

module.exports = addLineNumbers
function addLineNumbers (string, start, delim) {
  start = typeof start === 'number' ? start : 1
  delim = delim || ': '

  var lines = string.split(/\r?\n/)
  var totalDigits = String(lines.length + start - 1).length
  return lines.map(function (line, i) {
    var c = i + start
    var digits = String(c).length
    var prefix = padLeft(c, totalDigits - digits)
    return prefix + delim + line
  }).join('\n')
}