PHP's array_splice in JavaScript

How to use

You you can install via yarn add locutus and require this function via const array_splice = require('locutus/php/array/array_splice').

It is important to use a bundler that supports tree-shaking so that you only ship the functions that you actually use to your browser, instead of all of Locutus, which is massive. Examples are: Parcel, webpack, or rollup.js. For server-side use this is typically less of a concern.

Examples

Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#	code	expected result
1	var $input = {4: "red", 'abc': "green", 2: "blue", 'dud': "yellow"} array_splice($input, 2)	{4: "red", 'abc': "green"}
2	var $input = ["red", "green", "blue", "yellow"] array_splice($input, 3, 0, "purple")	[]
3	var $input = ["red", "green", "blue", "yellow"] array_splice($input, -1, 1, ["black", "maroon"])	["yellow"]

PHP arrays and JavaScript

Please note that Locutus uses 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 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.

So don't use this for anything serious if you rely on the order to be consistent accross platforms.

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

Notes

• Order does get shifted in associative array input with numeric indices, since PHP behavior doesn’t preserve keys, but I understand order is not reliable anyways Note also that IE retains information about property position even after being supposedly deleted, so use of this function may produce unexpected results in IE if you later attempt to add back properties with the same keys that had been deleted

Here’s what our current JavaScript equivalent to PHP's array_splice looks like.

module.exports = function array_splice(arr, offst, lgth, replacement) {
  //  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')

  const _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
  } else if (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)
    return Array.prototype.splice.apply(arr, replacement)
  }

  return arr.splice(offst, lgth)
}

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we assimilate first iterations with imperfections, hoping for others to take issue with-and improve them. This unorthodox approach has worked very well to foster fun and fruitful collaboration, but please be reminded to use our creations at your own risk. THE SOFTWARE IS PROVIDED "AS IS" has never been more true than for Locutus.

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