module.exports = function soundex(str) {
  //  discuss at: https://locutus.io/php/soundex/
  // original by: Jonas Raoni Soares Silva (https://www.jsfromhell.com)
  // original by: Arnout Kazemier (https://www.3rd-Eden.com)
  // improved by: Jack
  // improved by: Kevin van Zonneveld (https://kvz.io)
  // bugfixed by: Onno Marsman (https://twitter.com/onnomarsman)
  // bugfixed by: Kevin van Zonneveld (https://kvz.io)
  //    input by: Brett Zamir (https://brett-zamir.me)
  //  revised by: Rafał Kukawski (https://blog.kukawski.pl)
  //   example 1: soundex('Kevin')
  //   returns 1: 'K150'
  //   example 2: soundex('Ellery')
  //   returns 2: 'E460'
  //   example 3: soundex('Euler')
  //   returns 3: 'E460'

  str = (str + '').toUpperCase()
  if (!str) {
    return ''
  }

  const sdx = [0, 0, 0, 0]
  const m = {
    B: 1,
    F: 1,
    P: 1,
    V: 1,
    C: 2,
    G: 2,
    J: 2,
    K: 2,
    Q: 2,
    S: 2,
    X: 2,
    Z: 2,
    D: 3,
    T: 3,
    L: 4,
    M: 5,
    N: 5,
    R: 6,
  }
  let i = 0
  let j
  let s = 0
  let c
  let p

  while ((c = str.charAt(i++)) && s < 4) {
    if ((j = m[c])) {
      if (j !== p) {
        sdx[s++] = p = j
      }
    } else {
      s += i === 1
      p = 0
    }
  }

  sdx[0] = str.charAt(0)

  return sdx.join('')
}