Printer Errors.js

// In a factory a printer prints labels for boxes. For one kind of boxes the printer has to use colors which, for the sake of simplicity, are named with letters from a to m.

// The colors used by the printer are recorded in a control string. For example a "good" control string would be aaabbbbhaijjjm meaning that the printer used three times color a, four times color b, one time color h then one time color a...

// Sometimes there are problems: lack of colors, technical malfunction and a "bad" control string is produced e.g. aaaxbbbbyyhwawiwjjjwwm with letters not from a to m.

// You have to write a function printer_error which given a string will output the error rate of the printer as a string representing a rational whose numerator is the number of errors and the denominator the length of the control string. Don't reduce this fraction to a simpler expression.

// The string has a length greater or equal to one and contains only letters from ato z.

// #Examples:

// s="aaabbbbhaijjjm"
// error_printer(s) => "0/14"

// s="aaaxbbbbyyhwawiwjjjwwm"
// error_printer(s) => "8/22"

function printerError(s) {
  let numerator = 0
  s = s.replace(/[n-z]/g, (s) => {
    ++numerator
    return s
  })

  return numerator + '/' + s.length
}

var s = 'aaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbmmmmmmmmmmmmmmmmmmmxyz'
console.log(printerError(s), '3/56')