PHP's array_slice in TypeScript

How to use

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

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

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	array_slice(["a", "b", "c", "d", "e"], 2, -1)	[ 'c', 'd' ]
2	array_slice(["a", "b", "c", "d", "e"], 2, -1, true)	{2: 'c', 3: 'd'}

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

• Relies on is_int because !isNaN accepts floats

Dependencies

This function uses the following Locutus functions:

• is_int (php/var)

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

TSTypeScript JSJavaScript TSStandalone TS JSStandalone JS

Copy code

import type { PhpAssoc, PhpRuntimeValue } from '../_helpers/_phpTypes.ts'
import { is_int as isInt } from '../var/is_int.ts'

type SliceValue = PhpRuntimeValue

export function array_slice<TValue extends SliceValue>(
  arr: TValue[],
  offst: number,
  lgth?: number,
  preserveKeys?: false | undefined,
): TValue[]
export function array_slice<TValue extends SliceValue>(
  arr: TValue[],
  offst: number,
  lgth: number | undefined,
  preserveKeys: true,
): TValue[] | PhpAssoc<TValue | undefined>
export function array_slice<TValue extends SliceValue>(
  arr: PhpAssoc<TValue>,
  offst: number,
  lgth?: number,
  preserveKeys?: boolean,
): PhpAssoc<TValue | undefined>
export function array_slice<TValue extends SliceValue>(
  arr: TValue[] | PhpAssoc<TValue>,
  offst: number,
  lgth?: number,
  preserveKeys?: boolean,
): TValue[] | PhpAssoc<TValue | undefined> {
  //      discuss at: https://locutus.io/php/array_slice/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //        input by: Brett Zamir (https://brett-zamir.me)
  //     bugfixed by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Relies on is_int because !isNaN accepts floats
  //       example 1: array_slice(["a", "b", "c", "d", "e"], 2, -1)
  //       returns 1: [ 'c', 'd' ]
  //       example 2: array_slice(["a", "b", "c", "d", "e"], 2, -1, true)
  //       returns 2: {2: 'c', 3: 'd'}

  const preserve = preserveKeys === true
  let result: TValue[] | PhpAssoc<TValue | undefined>

  if (Array.isArray(arr) && !(preserve && offst !== 0)) {
    if (lgth === undefined) {
      result = arr.slice(offst)
    } else if (lgth >= 0) {
      result = arr.slice(offst, offst + lgth)
    } else {
      result = arr.slice(offst, lgth)
    }
  } else {
    const sourceAssoc: PhpAssoc<TValue | undefined> = {}
    let sourceLength = 0

    if (Array.isArray(arr)) {
      for (let index = 0; index < arr.length; index += 1) {
        sourceLength += 1
        sourceAssoc[String(index)] = arr[index]
      }
    } else {
      for (const key in arr) {
        sourceLength += 1
        sourceAssoc[key] = arr[key]
      }
    }

    const normalizedOffset = offst < 0 ? sourceLength + offst : offst
    const resolvedLength = lgth === undefined ? sourceLength : lgth < 0 ? sourceLength + lgth - normalizedOffset : lgth

    const sliced: PhpAssoc<TValue | undefined> = {}
    let started = false
    let sourceIndex = -1
    let collected = 0
    let sequentialKey = 0

    for (const key in sourceAssoc) {
      sourceIndex += 1

      if (collected >= resolvedLength) {
        break
      }

      if (sourceIndex === normalizedOffset) {
        started = true
      }

      if (!started) {
        continue
      }

      collected += 1

      if (isInt(key) && !preserve) {
        sliced[String(sequentialKey)] = sourceAssoc[key]
        sequentialKey += 1
      } else {
        sliced[key] = sourceAssoc[key]
      }
    }

    result = sliced
  }

  return result
}

import { is_int as isInt } from '../var/is_int.ts'
export function array_slice(arr, offst, lgth, preserveKeys) {
  //      discuss at: https://locutus.io/php/array_slice/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //        input by: Brett Zamir (https://brett-zamir.me)
  //     bugfixed by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Relies on is_int because !isNaN accepts floats
  //       example 1: array_slice(["a", "b", "c", "d", "e"], 2, -1)
  //       returns 1: [ 'c', 'd' ]
  //       example 2: array_slice(["a", "b", "c", "d", "e"], 2, -1, true)
  //       returns 2: {2: 'c', 3: 'd'}

  const preserve = preserveKeys === true
  let result

  if (Array.isArray(arr) && !(preserve && offst !== 0)) {
    if (lgth === undefined) {
      result = arr.slice(offst)
    } else if (lgth >= 0) {
      result = arr.slice(offst, offst + lgth)
    } else {
      result = arr.slice(offst, lgth)
    }
  } else {
    const sourceAssoc = {}
    let sourceLength = 0

    if (Array.isArray(arr)) {
      for (let index = 0; index < arr.length; index += 1) {
        sourceLength += 1
        sourceAssoc[String(index)] = arr[index]
      }
    } else {
      for (const key in arr) {
        sourceLength += 1
        sourceAssoc[key] = arr[key]
      }
    }

    const normalizedOffset = offst < 0 ? sourceLength + offst : offst
    const resolvedLength = lgth === undefined ? sourceLength : lgth < 0 ? sourceLength + lgth - normalizedOffset : lgth

    const sliced = {}
    let started = false
    let sourceIndex = -1
    let collected = 0
    let sequentialKey = 0

    for (const key in sourceAssoc) {
      sourceIndex += 1

      if (collected >= resolvedLength) {
        break
      }

      if (sourceIndex === normalizedOffset) {
        started = true
      }

      if (!started) {
        continue
      }

      collected += 1

      if (isInt(key) && !preserve) {
        sliced[String(sequentialKey)] = sourceAssoc[key]
        sequentialKey += 1
      } else {
        sliced[key] = sourceAssoc[key]
      }
    }

    result = sliced
  }

  return result
}

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

type PhpInput = {} | PhpNullish

type PhpScalar = string | number | boolean

type PhpPrimitive = PhpScalar | bigint

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

type PhpFunctionValue = (...args: PhpInput[]) => PhpInput

interface PhpRuntimeAssoc {
  [key: string]: PhpRuntimeValue
}

interface PhpRuntimeList extends Array<PhpRuntimeValue> {}

type PhpRuntimeValue = PhpPrimitive | PhpNullish | PhpRuntimeList | PhpRuntimeAssoc | PhpFunctionValue

// php/var/is_int (Locutus dependency module)
type IntValue = PhpRuntimeValue

function is_int(mixedVar: IntValue): mixedVar is number {
  //      discuss at: https://locutus.io/php/is_int/
  // parity verified: PHP 8.3
  //     original by: Alex
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: WebDevHobo (https://webdevhobo.blogspot.com/)
  //     improved by: Rafał Kukawski (https://blog.kukawski.pl)
  //      revised by: Matt Bradley
  //     bugfixed by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: 1.0 is simplified to 1 before it can be accessed by the function, this makes
  //          note 1: it different from the PHP implementation. We can't fix this unfortunately.
  //       example 1: is_int(23)
  //       returns 1: true
  //       example 2: is_int('23')
  //       returns 2: false
  //       example 3: is_int(23.5)
  //       returns 3: false
  //       example 4: is_int(true)
  //       returns 4: false

  const num = Number(mixedVar)
  return typeof mixedVar === 'number' && mixedVar === num && Number.isFinite(num) && Number.isInteger(num)
}

// php/array/array_slice (target function module)
const isInt = is_int;

type SliceValue = PhpRuntimeValue

function array_slice<TValue extends SliceValue>(
  arr: TValue[],
  offst: number,
  lgth?: number,
  preserveKeys?: false | undefined,
): TValue[]

function array_slice<TValue extends SliceValue>(
  arr: TValue[],
  offst: number,
  lgth: number | undefined,
  preserveKeys: true,
): TValue[] | PhpAssoc<TValue | undefined>

function array_slice<TValue extends SliceValue>(
  arr: PhpAssoc<TValue>,
  offst: number,
  lgth?: number,
  preserveKeys?: boolean,
): PhpAssoc<TValue | undefined>

function array_slice<TValue extends SliceValue>(
  arr: TValue[] | PhpAssoc<TValue>,
  offst: number,
  lgth?: number,
  preserveKeys?: boolean,
): TValue[] | PhpAssoc<TValue | undefined> {
  //      discuss at: https://locutus.io/php/array_slice/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //        input by: Brett Zamir (https://brett-zamir.me)
  //     bugfixed by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Relies on is_int because !isNaN accepts floats
  //       example 1: array_slice(["a", "b", "c", "d", "e"], 2, -1)
  //       returns 1: [ 'c', 'd' ]
  //       example 2: array_slice(["a", "b", "c", "d", "e"], 2, -1, true)
  //       returns 2: {2: 'c', 3: 'd'}

  const preserve = preserveKeys === true
  let result: TValue[] | PhpAssoc<TValue | undefined>

  if (Array.isArray(arr) && !(preserve && offst !== 0)) {
    if (lgth === undefined) {
      result = arr.slice(offst)
    } else if (lgth >= 0) {
      result = arr.slice(offst, offst + lgth)
    } else {
      result = arr.slice(offst, lgth)
    }
  } else {
    const sourceAssoc: PhpAssoc<TValue | undefined> = {}
    let sourceLength = 0

    if (Array.isArray(arr)) {
      for (let index = 0; index < arr.length; index += 1) {
        sourceLength += 1
        sourceAssoc[String(index)] = arr[index]
      }
    } else {
      for (const key in arr) {
        sourceLength += 1
        sourceAssoc[key] = arr[key]
      }
    }

    const normalizedOffset = offst < 0 ? sourceLength + offst : offst
    const resolvedLength = lgth === undefined ? sourceLength : lgth < 0 ? sourceLength + lgth - normalizedOffset : lgth

    const sliced: PhpAssoc<TValue | undefined> = {}
    let started = false
    let sourceIndex = -1
    let collected = 0
    let sequentialKey = 0

    for (const key in sourceAssoc) {
      sourceIndex += 1

      if (collected >= resolvedLength) {
        break
      }

      if (sourceIndex === normalizedOffset) {
        started = true
      }

      if (!started) {
        continue
      }

      collected += 1

      if (isInt(key) && !preserve) {
        sliced[String(sequentialKey)] = sourceAssoc[key]
        sequentialKey += 1
      } else {
        sliced[key] = sourceAssoc[key]
      }
    }

    result = sliced
  }

  return result
}

// php/var/is_int (Locutus dependency module)
function is_int(mixedVar) {
  //      discuss at: https://locutus.io/php/is_int/
  // parity verified: PHP 8.3
  //     original by: Alex
  //     improved by: Kevin van Zonneveld (https://kvz.io)
  //     improved by: WebDevHobo (https://webdevhobo.blogspot.com/)
  //     improved by: Rafał Kukawski (https://blog.kukawski.pl)
  //      revised by: Matt Bradley
  //     bugfixed by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: 1.0 is simplified to 1 before it can be accessed by the function, this makes
  //          note 1: it different from the PHP implementation. We can't fix this unfortunately.
  //       example 1: is_int(23)
  //       returns 1: true
  //       example 2: is_int('23')
  //       returns 2: false
  //       example 3: is_int(23.5)
  //       returns 3: false
  //       example 4: is_int(true)
  //       returns 4: false

  const num = Number(mixedVar)
  return typeof mixedVar === 'number' && mixedVar === num && Number.isFinite(num) && Number.isInteger(num)
}

// php/array/array_slice (target function module)
const isInt = is_int

function array_slice(arr, offst, lgth, preserveKeys) {
  //      discuss at: https://locutus.io/php/array_slice/
  // parity verified: PHP 8.3
  //     original by: Brett Zamir (https://brett-zamir.me)
  //        input by: Brett Zamir (https://brett-zamir.me)
  //     bugfixed by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Relies on is_int because !isNaN accepts floats
  //       example 1: array_slice(["a", "b", "c", "d", "e"], 2, -1)
  //       returns 1: [ 'c', 'd' ]
  //       example 2: array_slice(["a", "b", "c", "d", "e"], 2, -1, true)
  //       returns 2: {2: 'c', 3: 'd'}

  const preserve = preserveKeys === true
  let result

  if (Array.isArray(arr) && !(preserve && offst !== 0)) {
    if (lgth === undefined) {
      result = arr.slice(offst)
    } else if (lgth >= 0) {
      result = arr.slice(offst, offst + lgth)
    } else {
      result = arr.slice(offst, lgth)
    }
  } else {
    const sourceAssoc = {}
    let sourceLength = 0

    if (Array.isArray(arr)) {
      for (let index = 0; index < arr.length; index += 1) {
        sourceLength += 1
        sourceAssoc[String(index)] = arr[index]
      }
    } else {
      for (const key in arr) {
        sourceLength += 1
        sourceAssoc[key] = arr[key]
      }
    }

    const normalizedOffset = offst < 0 ? sourceLength + offst : offst
    const resolvedLength = lgth === undefined ? sourceLength : lgth < 0 ? sourceLength + lgth - normalizedOffset : lgth

    const sliced = {}
    let started = false
    let sourceIndex = -1
    let collected = 0
    let sequentialKey = 0

    for (const key in sourceAssoc) {
      sourceIndex += 1

      if (collected >= resolvedLength) {
        break
      }

      if (sourceIndex === normalizedOffset) {
        started = true
      }

      if (!started) {
        continue
      }

      collected += 1

      if (isInt(key) && !preserve) {
        sliced[String(sequentialKey)] = sourceAssoc[key]
        sequentialKey += 1
      } else {
        sliced[key] = sourceAssoc[key]
      }
    }

    result = sliced
  }

  return result
}

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