PHP's str_word_count in JavaScript

module.exports = functionstr_word_count (str, format, charlist) { // eslint-disable-line camelcase
//  discuss at: https://locutus.io/php/str_word_count/
// original by: Ole Vrijenhoek
// bugfixed by: Kevin van Zonneveld (https://kvz.io)
// bugfixed by: Brett Zamir (https://brett-zamir.me)
// bugfixed by: Brett Zamir (https://brett-zamir.me)
//    input by: Bug?
// improved by: Brett Zamir (https://brett-zamir.me)
//   example 1: str_word_count("Hello fri3nd, you're\r\n       looking          good today!", 1)
//   returns 1: ['Hello', 'fri', 'nd', "you're", 'looking', 'good', 'today']
//   example 2: str_word_count("Hello fri3nd, you're\r\n       looking          good today!", 2)
//   returns 2: {0: 'Hello', 6: 'fri', 10: 'nd', 14: "you're", 29: 'looking', 46: 'good', 51: 'today'}
//   example 3: str_word_count("Hello fri3nd, you're\r\n       looking          good today!", 1, '\u00e0\u00e1\u00e3\u00e73')
//   returns 3: ['Hello', 'fri3nd', "you're", 'looking', 'good', 'today']
//   example 4: str_word_count('hey', 2)
//   returns 4: {0: 'hey'}
const ctypeAlpha = require('../ctype/ctype_alpha')
const len = str.length
const cl = charlist && charlist.length
let chr = ''
let tmpStr = ''
let i = 0
let c = ''
const wArr = []
let wC = 0
const assoc = {}
let aC = 0
let reg = ''
let match = false
const _pregQuote = function (str) {
return (str + '').replace(/([\\.+*?[^\]$(){}=!<>|:])/g, '\\$1')
  }
const _getWholeChar = function (str, i) {
// Use for rare cases of non-BMP characters
const code = str.charCodeAt(i)
if (code < 0xD800 || code > 0xDFFF) {
return str.charAt(i)
    }
if (code >= 0xD800 && code <= 0xDBFF) {
// High surrogate (could change last hex to 0xDB7F to treat high private surrogates as single
// characters)
if (str.length <= (i + 1)) {
thrownewError('High surrogate without following low surrogate')
      }
const next = str.charCodeAt(i + 1)
if (next < 0xDC00 || next > 0xDFFF) {
thrownewError('High surrogate without following low surrogate')
      }
return str.charAt(i) + str.charAt(i + 1)
    }
// Low surrogate (0xDC00 <= code && code <= 0xDFFF)
if (i === 0) {
thrownewError('Low surrogate without preceding high surrogate')
    }
const prev = str.charCodeAt(i - 1)
if (prev < 0xD800 || prev > 0xDBFF) {
// (could change last hex to 0xDB7F to treat high private surrogates as single characters)
thrownewError('Low surrogate without preceding high surrogate')
    }
// We can pass over low surrogates now as the second component in a pair which we have already
// processed
returnfalse
  }
if (cl) {
    reg = '^(' + _pregQuote(_getWholeChar(charlist, 0))
for (i = 1; i < cl; i++) {
if ((chr = _getWholeChar(charlist, i)) === false) {
continue
      }
      reg += '|' + _pregQuote(chr)
    }
    reg += ')$'
    reg = newRegExp(reg)
  }
for (i = 0; i < len; i++) {
if ((c = _getWholeChar(str, i)) === false) {
continue
    }
// No hyphen at beginning or end unless allowed in charlist (or locale)
// No apostrophe at beginning unless allowed in charlist (or locale)
// @todo: Make this more readable
    match = ctypeAlpha(c) ||
      (reg && c.search(reg) !== -1) ||
      ((i !== 0 && i !== len - 1) && c === '-') ||
      (i !== 0 && c === "'")
if (match) {
if (tmpStr === '' && format === 2) {
        aC = i
      }
      tmpStr = tmpStr + c
    }
if (i === len - 1 || !match && tmpStr !== '') {
if (format !== 2) {
        wArr[wArr.length] = tmpStr
      } else {
        assoc[aC] = tmpStr
      }
      tmpStr = ''
      wC++
    }
  }
if (!format) {
return wC
  } elseif (format === 1) {
return wArr
  } elseif (format === 2) {
return assoc
  }
thrownewError('You have supplied an incorrect format')
}