PHP's array_splice in JavaScript

module.exports = functionarray_splice (arr, offst, lgth, replacement) { // eslint-disable-line camelcase
//  discuss at: https://locutus.io/php/array_splice/
// original by: Brett Zamir (https://brett-zamir.me)
//    input by: Theriault (https://github.com/Theriault)
//      note 1: Order does get shifted in associative array input with numeric indices,
//      note 1: since PHP behavior doesn't preserve keys, but I understand order is
//      note 1: not reliable anyways
//      note 1: Note also that IE retains information about property position even
//      note 1: after being supposedly deleted, so use of this function may produce
//      note 1: unexpected results in IE if you later attempt to add back properties
//      note 1: with the same keys that had been deleted
//   example 1: var $input = {4: "red", 'abc': "green", 2: "blue", 'dud': "yellow"}
//   example 1: array_splice($input, 2)
//   returns 1: {4: "red", 'abc': "green"}
//   example 2: var $input = ["red", "green", "blue", "yellow"]
//   example 2: array_splice($input, 3, 0, "purple")
//   returns 2: []
//   example 3: var $input = ["red", "green", "blue", "yellow"]
//   example 3: array_splice($input, -1, 1, ["black", "maroon"])
//   returns 3: ["yellow"]
//        test: skip-1
const isInt = require('../var/is_int')
var _checkToUpIndices = function (arr, ct, key) {
// Deal with situation, e.g., if encounter index 4 and try
// to set it to 0, but 0 exists later in loop (need to
// increment all subsequent (skipping current key,
// since we need its value below) until find unused)
if (arr[ct] !== undefined) {
const tmp = ct
      ct += 1
if (ct === key) {
        ct += 1
      }
      ct = _checkToUpIndices(arr, ct, key)
      arr[ct] = arr[tmp]
delete arr[tmp]
    }
return ct
  }
if (replacement && typeof replacement !== 'object') {
    replacement = [replacement]
  }
if (lgth === undefined) {
    lgth = offst >= 0 ? arr.length - offst : -offst
  } elseif (lgth < 0) {
    lgth = (offst >= 0 ? arr.length - offst : -offst) + lgth
  }
if (Object.prototype.toString.call(arr) !== '[object Array]') {
/* if (arr.length !== undefined) {
     // Deal with array-like objects as input
    delete arr.length;
    } */
let lgt = 0
let ct = -1
const rmvd = []
const rmvdObj = {}
let replCt = -1
let intCt = -1
let returnArr = true
let rmvdCt = 0
// var rmvdLngth = 0
let key = ''
// rmvdObj.length = 0;
for (key in arr) {
// Can do arr.__count__ in some browsers
      lgt += 1
    }
    offst = (offst >= 0) ? offst : lgt + offst
for (key in arr) {
      ct += 1
if (ct < offst) {
if (isInt(key)) {
          intCt += 1
if (parseInt(key, 10) === intCt) {
// Key is already numbered ok, so don't need to change key for value
continue
          }
// Deal with situation, e.g.,
          _checkToUpIndices(arr, intCt, key)
// if encounter index 4 and try to set it to 0, but 0 exists later in loop
          arr[intCt] = arr[key]
delete arr[key]
        }
continue
      }
if (returnArr && isInt(key)) {
        rmvd.push(arr[key])
// PHP starts over here too
        rmvdObj[rmvdCt++] = arr[key]
      } else {
        rmvdObj[key] = arr[key]
        returnArr = false
      }
// rmvdLngth += 1
// rmvdObj.length += 1;
if (replacement && replacement[++replCt]) {
        arr[key] = replacement[replCt]
      } else {
delete arr[key]
      }
    }
// Make (back) into an array-like object
// arr.length = lgt - rmvdLngth + (replacement ? replacement.length : 0);
return returnArr ? rmvd : rmvdObj
  }
if (replacement) {
    replacement.unshift(offst, lgth)
returnArray.prototype.splice.apply(arr, replacement)
  }
return arr.splice(offst, lgth)
}