PHP's strtr in JavaScript

module.exports = functionstrtr (str, trFrom, trTo) {
//  discuss at: https://locutus.io/php/strtr/
// original by: Brett Zamir (https://brett-zamir.me)
//    input by: uestla
//    input by: Alan C
//    input by: Taras Bogach
//    input by: jpfle
// bugfixed by: Kevin van Zonneveld (https://kvz.io)
// bugfixed by: Kevin van Zonneveld (https://kvz.io)
// bugfixed by: Brett Zamir (https://brett-zamir.me)
// bugfixed by: Brett Zamir (https://brett-zamir.me)
//   example 1: var $trans = {'hello' : 'hi', 'hi' : 'hello'}
//   example 1: strtr('hi all, I said hello', $trans)
//   returns 1: 'hello all, I said hi'
//   example 2: strtr('äaabaåccasdeöoo', 'äåö','aao')
//   returns 2: 'aaabaaccasdeooo'
//   example 3: strtr('ääääääää', 'ä', 'a')
//   returns 3: 'aaaaaaaa'
//   example 4: strtr('http', 'pthxyz','xyzpth')
//   returns 4: 'zyyx'
//   example 5: strtr('zyyx', 'pthxyz','xyzpth')
//   returns 5: 'http'
//   example 6: strtr('aa', {'a':1,'aa':2})
//   returns 6: '2'
const krsort = require('../array/krsort')
const iniSet = require('../info/ini_set')
let fr = ''
let i = 0
let j = 0
let lenStr = 0
let lenFrom = 0
let sortByReference = false
let fromTypeStr = ''
let toTypeStr = ''
let istr = ''
const tmpFrom = []
const tmpTo = []
let ret = ''
let match = false
// Received replace_pairs?
// Convert to normal trFrom->trTo chars
if (typeof trFrom === 'object') {
// Not thread-safe; temporarily set to true
// @todo: Don't rely on ini here, use internal krsort instead
    sortByReference = iniSet('locutus.sortByReference', false)
    trFrom = krsort(trFrom)
    iniSet('locutus.sortByReference', sortByReference)
for (fr in trFrom) {
if (trFrom.hasOwnProperty(fr)) {
        tmpFrom.push(fr)
        tmpTo.push(trFrom[fr])
      }
    }
    trFrom = tmpFrom
    trTo = tmpTo
  }
// Walk through subject and replace chars when needed
  lenStr = str.length
  lenFrom = trFrom.length
  fromTypeStr = typeof trFrom === 'string'
  toTypeStr = typeof trTo === 'string'
for (i = 0; i < lenStr; i++) {
    match = false
if (fromTypeStr) {
      istr = str.charAt(i)
for (j = 0; j < lenFrom; j++) {
if (istr === trFrom.charAt(j)) {
          match = true
break
        }
      }
    } else {
for (j = 0; j < lenFrom; j++) {
if (str.substr(i, trFrom[j].length) === trFrom[j]) {
          match = true
// Fast forward
          i = (i + trFrom[j].length) - 1
break
        }
      }
    }
if (match) {
      ret += toTypeStr ? trTo.charAt(j) : trTo[j]
    } else {
      ret += str.charAt(i)
    }
  }
return ret
}