PHP's serialize in JavaScript

module.exports = functionserialize (mixedValue) {
//  discuss at: https://locutus.io/php/serialize/
// original by: Arpad Ray (mailto:arpad@php.net)
// improved by: Dino
// improved by: Le Torbi (https://www.letorbi.de/)
// improved by: Kevin van Zonneveld (https://kvz.io/)
// bugfixed by: Andrej Pavlovic
// bugfixed by: Garagoth
// bugfixed by: Russell Walker (https://www.nbill.co.uk/)
// bugfixed by: Jamie Beck (https://www.terabit.ca/)
// bugfixed by: Kevin van Zonneveld (https://kvz.io/)
// bugfixed by: Ben (https://benblume.co.uk/)
// bugfixed by: Codestar (https://codestarlive.com/)
// bugfixed by: idjem (https://github.com/idjem)
//    input by: DtTvB (https://dt.in.th/2008-09-16.string-length-in-bytes.html)
//    input by: Martin (https://www.erlenwiese.de/)
//      note 1: We feel the main purpose of this function should be to ease
//      note 1: the transport of data between php & js
//      note 1: Aiming for PHP-compatibility, we have to translate objects to arrays
//   example 1: serialize(['Kevin', 'van', 'Zonneveld'])
//   returns 1: 'a:3:{i:0;s:5:"Kevin";i:1;s:3:"van";i:2;s:9:"Zonneveld";}'
//   example 2: serialize({firstName: 'Kevin', midName: 'van'})
//   returns 2: 'a:2:{s:9:"firstName";s:5:"Kevin";s:7:"midName";s:3:"van";}'
//   example 3: serialize( {'ü': 'ü', '四': '四', '𠜎': '𠜎'})
//   returns 3: 'a:3:{s:2:"ü";s:2:"ü";s:3:"四";s:3:"四";s:4:"𠜎";s:4:"𠜎";}'
let val, key, okey
let ktype = ''
let vals = ''
let count = 0
const _utf8Size = function (str) {
return ~-encodeURI(str).split(/%..|./).length
  }
const _getType = function (inp) {
let match
let key
let cons
let types
let type = typeof inp
if (type === 'object' && !inp) {
return'null'
    }
if (type === 'object') {
if (!inp.constructor) {
return'object'
      }
      cons = inp.constructor.toString()
      match = cons.match(/(\w+)\(/)
if (match) {
        cons = match[1].toLowerCase()
      }
      types = ['boolean', 'number', 'string', 'array']
for (key in types) {
if (cons === types[key]) {
          type = types[key]
break
        }
      }
    }
return type
  }
const type = _getType(mixedValue)
switch (type) {
case'function':
      val = ''
break
case'boolean':
      val = 'b:' + (mixedValue ? '1' : '0')
break
case'number':
      val = (Math.round(mixedValue) === mixedValue ? 'i' : 'd') + ':' + mixedValue
break
case'string':
      val = 's:' + _utf8Size(mixedValue) + ':"' + mixedValue + '"'
break
case'array':
case'object':
      val = 'a'
/*
      if (type === 'object') {
        var objname = mixedValue.constructor.toString().match(/(\w+)\(\)/);
        if (objname === undefined) {
          return;
        }
        objname[1] = serialize(objname[1]);
        val = 'O' + objname[1].substring(1, objname[1].length - 1);
      }
      */
for (key in mixedValue) {
if (mixedValue.hasOwnProperty(key)) {
          ktype = _getType(mixedValue[key])
if (ktype === 'function') {
continue
          }
          okey = (key.match(/^[0-9]+$/) ? parseInt(key, 10) : key)
          vals += serialize(okey) + serialize(mixedValue[key])
          count++
        }
      }
      val += ':' + count + ':{' + vals + '}'
break
case'undefined':
default:
// Fall-through
// if the JS object has a property which contains a null value,
// the string cannot be unserialized by PHP
      val = 'N'
break
  }
if (type !== 'object' && type !== 'array') {
    val += ';'
  }
return val
}