PHP's next in TypeScript

How to use

Install via yarn add locutus and import: import { next } from 'locutus/php/array/next'.

Or with CommonJS: const { next } = require('locutus/php/array/next')

Use a bundler that supports tree-shaking so you only ship the functions you actually use. Vite, webpack, Rollup, and Parcel all handle this. For server-side use this is less of a concern.

Examples

These examples are extracted from test cases that automatically verify our functions against their native counterparts.

#	code	expected result
1	var $transport = ['foot', 'bike', 'car', 'plane'] next($transport) next($transport)	'car'

PHP arrays and TypeScript/JavaScript

Please note that Locutus uses TypeScript/JavaScript objects as substitutes for PHP arrays, they are the closest we can get to this hashtable-like data structure without rolling our own. While many TypeScript/JavaScript implementations preserve the order of object properties, the ECMAScript Language Specification explicitly states that:

The mechanics and order of enumerating the properties is not specified.

In practice most engines preserve insertion order, but if your code depends on key ordering across platforms, keep this caveat in mind.

To influence how Locutus treats objects as arrays, you can check out the locutus.objectsAsArrays setting.

Notes

• Uses global: locutus to store the array pointer

Dependencies

This function uses the following Locutus functions:

• _arrayPointers (php/_helpers)

Here's what our current TypeScript equivalent to PHP's next looks like.

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

import { getEntryAtCursor, getPointerState } from '../_helpers/_arrayPointers.ts'
import type { PhpArrayLike } from '../_helpers/_phpTypes.ts'

export function next<T>(arr: PhpArrayLike<T>): T | false {
  //      discuss at: https://locutus.io/php/next/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //          note 1: Uses global: locutus to store the array pointer
  //       example 1: var $transport = ['foot', 'bike', 'car', 'plane']
  //       example 1: next($transport)
  //       example 1: next($transport)
  //       returns 1: 'car'

  const state = getPointerState(arr, true)
  if (!state) {
    return false
  }

  const nextCursor = state.cursor + 1
  const entry = getEntryAtCursor(arr, nextCursor)
  if (!entry) {
    return false
  }

  state.setCursor(nextCursor)
  return entry[1]
}

import { getEntryAtCursor, getPointerState } from '../_helpers/_arrayPointers.ts'

export function next(arr) {
  //      discuss at: https://locutus.io/php/next/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //          note 1: Uses global: locutus to store the array pointer
  //       example 1: var $transport = ['foot', 'bike', 'car', 'plane']
  //       example 1: next($transport)
  //       example 1: next($transport)
  //       returns 1: 'car'

  const state = getPointerState(arr, true)
  if (!state) {
    return false
  }

  const nextCursor = state.cursor + 1
  const entry = getEntryAtCursor(arr, nextCursor)
  if (!entry) {
    return false
  }

  state.setCursor(nextCursor)
  return entry[1]
}

// php/_helpers/_phpTypes (Locutus helper dependency)
type PhpNullish = null | undefined

type PhpInput = {} | PhpNullish

type PhpList<T = PhpInput> = T[]

type PhpAssoc<T = PhpInput> = { [key: string]: T }

type PhpArrayLike<T = PhpInput> = PhpList<T> | PhpAssoc<T>

const entriesOfPhpAssoc = <T>(value: PhpAssoc<T>): Array<[string, T]> => {
  return Object.entries(value)
}

function isPhpList<T = PhpInput>(value: PhpInput): value is PhpList<T> {
  return Array.isArray(value)
}

function isObjectLike(value: PhpInput): value is PhpArrayLike<PhpInput> {
  return typeof value === 'object' && value !== null
}

function isPhpAssocObject<T = PhpInput>(value: PhpInput): value is PhpAssoc<T> {
  return isObjectLike(value) && !isPhpList(value)
}

// php/_helpers/_phpRuntimeState (Locutus helper dependency)
interface IniEntry {
  local_value?: PhpInput
}

type LocaleEntry = PhpAssoc<PhpInput> & {
  sorting?: (left: PhpInput, right: PhpInput) => number
}

type LocaleCategoryMap = PhpAssoc<string | undefined>

interface LocutusRuntimeContainer {
  php?: PhpAssoc<PhpInput>
}

type GlobalWithLocutus = {
  $locutus?: LocutusRuntimeContainer
  [key: string]: PhpInput
}

interface PhpRuntimeState {
  ini: PhpAssoc<IniEntry | undefined>
  locales: PhpAssoc<LocaleEntry | undefined>
  localeCategories: LocaleCategoryMap
  pointers: PhpList<PhpInput>
  locale_default: string | undefined
}

const isIniBag = (value: PhpInput): value is PhpAssoc<IniEntry | undefined> =>
  isPhpAssocObject<IniEntry | undefined>(value)

const isLocaleBag = (value: PhpInput): value is PhpAssoc<LocaleEntry | undefined> =>
  isPhpAssocObject<LocaleEntry | undefined>(value)

const isLocaleCategoryBag = (value: PhpInput): value is LocaleCategoryMap => isPhpAssocObject<string | undefined>(value)

const globalContext: GlobalWithLocutus =
  typeof window === 'object' && window !== null ? window : typeof global === 'object' && global !== null ? global : {}

const ensurePhpRuntimeObject = (): PhpAssoc<PhpInput> => {
  let locutus = globalContext.$locutus
  if (typeof locutus !== 'object' || locutus === null) {
    locutus = {}
    globalContext.$locutus = locutus
  }

  let php = locutus.php
  if (typeof php !== 'object' || php === null) {
    php = {}
    locutus.php = php
  }

  return php
}

function ensurePhpRuntimeState(): PhpRuntimeState {
  const php = ensurePhpRuntimeObject()
  const iniValue = php.ini
  const localesValue = php.locales
  const localeCategoriesValue = php.localeCategories
  const pointersValue = php.pointers

  const ini = isIniBag(iniValue) ? iniValue : {}
  const locales = isLocaleBag(localesValue) ? localesValue : {}
  const localeCategories = isLocaleCategoryBag(localeCategoriesValue) ? localeCategoriesValue : {}
  const pointers: PhpList<PhpInput> = Array.isArray(pointersValue) ? pointersValue : []

  if (iniValue !== ini) {
    php.ini = ini
  }
  if (localesValue !== locales) {
    php.locales = locales
  }
  if (localeCategoriesValue !== localeCategories) {
    php.localeCategories = localeCategories
  }
  if (pointersValue !== pointers) {
    php.pointers = pointers
  }

  const localeDefaultValue = php.locale_default
  const localeDefault = typeof localeDefaultValue === 'string' ? localeDefaultValue : undefined

  return {
    ini,
    locales,
    localeCategories,
    pointers,
    locale_default: localeDefault,
  }
}

// php/_helpers/_arrayPointers (Locutus helper dependency)
interface PointerState {
  cursor: number
  setCursor: (nextCursor: number) => void
}

const findPointerIndex = (pointers: PhpList<PhpInput>, target: PhpInput): number => {
  for (let index = 0; index < pointers.length; index += 1) {
    if (pointers[index] === target) {
      return index
    }
  }

  return -1
}

function getPointerState<T>(target: PhpArrayLike<T>, initialize = true): PointerState | null {
  const runtime = ensurePhpRuntimeState()
  const pointers = runtime.pointers
  // Store [target, cursor] pairs in one flat runtime list so pointer state stays bound to each array-like input.
  const pointerTarget: PhpInput = target

  let index = findPointerIndex(pointers, pointerTarget)
  if (index === -1) {
    if (!initialize) {
      return null
    }
    pointers.push(pointerTarget, 0)
    index = pointers.length - 2
  }

  const cursorValue = pointers[index + 1]
  const cursor = typeof cursorValue === 'number' ? cursorValue : 0

  return {
    cursor,
    setCursor: (nextCursor: number) => {
      pointers[index + 1] = nextCursor
    },
  }
}

function getEntryAtCursor<T>(target: PhpArrayLike<T>, cursor: number): [string | number, T] | null {
  if (cursor < 0) {
    return null
  }

  if (Array.isArray(target)) {
    if (cursor >= target.length) {
      return null
    }

    const value = target[cursor]
    if (typeof value === 'undefined') {
      return null
    }
    return [cursor, value]
  }

  let index = 0
  for (const [key, value] of entriesOfPhpAssoc(target)) {
    if (index === cursor) {
      return [key, value]
    }
    index += 1
  }

  return null
}

// php/array/next (target function module)
function next<T>(arr: PhpArrayLike<T>): T | false {
  //      discuss at: https://locutus.io/php/next/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //          note 1: Uses global: locutus to store the array pointer
  //       example 1: var $transport = ['foot', 'bike', 'car', 'plane']
  //       example 1: next($transport)
  //       example 1: next($transport)
  //       returns 1: 'car'

  const state = getPointerState(arr, true)
  if (!state) {
    return false
  }

  const nextCursor = state.cursor + 1
  const entry = getEntryAtCursor(arr, nextCursor)
  if (!entry) {
    return false
  }

  state.setCursor(nextCursor)
  return entry[1]
}

// php/_helpers/_phpTypes (Locutus helper dependency)

function isObjectLike(value) {
  return typeof value === 'object' && value !== null
}

function isPhpAssocObject(value) {
  return isObjectLike(value) && !Array.isArray(value)
}

// php/_helpers/_phpRuntimeState (Locutus helper dependency)

const globalContext =
  typeof window === 'object' && window !== null ? window : typeof global === 'object' && global !== null ? global : {}

const ensurePhpRuntimeObject = () => {
  let locutus = globalContext.$locutus
  if (typeof locutus !== 'object' || locutus === null) {
    locutus = {}
    globalContext.$locutus = locutus
  }

  let php = locutus.php
  if (typeof php !== 'object' || php === null) {
    php = {}
    locutus.php = php
  }

  return php
}

function ensurePhpRuntimeState() {
  const php = ensurePhpRuntimeObject()
  const iniValue = php.ini
  const localesValue = php.locales
  const localeCategoriesValue = php.localeCategories
  const pointersValue = php.pointers

  const ini = isPhpAssocObject(iniValue) ? iniValue : {}
  const locales = isPhpAssocObject(localesValue) ? localesValue : {}
  const localeCategories = isPhpAssocObject(localeCategoriesValue) ? localeCategoriesValue : {}
  const pointers = Array.isArray(pointersValue) ? pointersValue : []

  if (iniValue !== ini) {
    php.ini = ini
  }
  if (localesValue !== locales) {
    php.locales = locales
  }
  if (localeCategoriesValue !== localeCategories) {
    php.localeCategories = localeCategories
  }
  if (pointersValue !== pointers) {
    php.pointers = pointers
  }

  const localeDefaultValue = php.locale_default
  const localeDefault = typeof localeDefaultValue === 'string' ? localeDefaultValue : undefined

  return {
    ini,
    locales,
    localeCategories,
    pointers,
    locale_default: localeDefault,
  }
}

// php/_helpers/_arrayPointers (Locutus helper dependency)
const findPointerIndex = (pointers, target) => {
  for (let index = 0; index < pointers.length; index += 1) {
    if (pointers[index] === target) {
      return index
    }
  }

  return -1
}

function getPointerState(target, initialize = true) {
  const runtime = ensurePhpRuntimeState()
  const pointers = runtime.pointers
  // Store [target, cursor] pairs in one flat runtime list so pointer state stays bound to each array-like input.
  const pointerTarget = target

  let index = findPointerIndex(pointers, pointerTarget)
  if (index === -1) {
    if (!initialize) {
      return null
    }
    pointers.push(pointerTarget, 0)
    index = pointers.length - 2
  }

  const cursorValue = pointers[index + 1]
  const cursor = typeof cursorValue === 'number' ? cursorValue : 0

  return {
    cursor,
    setCursor: (nextCursor) => {
      pointers[index + 1] = nextCursor
    },
  }
}

function getEntryAtCursor(target, cursor) {
  if (cursor < 0) {
    return null
  }

  if (Array.isArray(target)) {
    if (cursor >= target.length) {
      return null
    }

    const value = target[cursor]
    if (typeof value === 'undefined') {
      return null
    }
    return [cursor, value]
  }

  let index = 0
  for (const [key, value] of Object.entries(target)) {
    if (index === cursor) {
      return [key, value]
    }
    index += 1
  }

  return null
}

// php/array/next (target function module)
function next(arr) {
  //      discuss at: https://locutus.io/php/next/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //          note 1: Uses global: locutus to store the array pointer
  //       example 1: var $transport = ['foot', 'bike', 'car', 'plane']
  //       example 1: next($transport)
  //       example 1: next($transport)
  //       returns 1: 'car'

  const state = getPointerState(arr, true)
  if (!state) {
    return false
  }

  const nextCursor = state.cursor + 1
  const entry = getEntryAtCursor(arr, nextCursor)
  if (!entry) {
    return false
  }

  state.setCursor(nextCursor)
  return entry[1]
}

Improve this function

Locutus is a community effort following The McDonald's Theory: we ship first iterations, hoping others will improve them. If you see something that could be better, we'd love your contribution.

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