PHP's array_splice in JavaScript

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

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module.exports = function array_splice (arr, offst, lgth, replacement) { // eslint-disable-line camelcase
// discuss at: http://locutus.io/php/array_splice/
// original by: Brett Zamir (http://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
var 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) {
var 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;
} */
var lgt = 0
var ct = -1
var rmvd = []
var rmvdObj = {}
var replCt = -1
var intCt = -1
var returnArr = true
var rmvdCt = 0
// var rmvdLngth = 0
var 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)
}
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How to use

You you can install via npm install locutus and require it via require('locutus/php/array/array_splice'). You could also require the array module in full so that you could access array.array_splice instead.

If you intend to target the browser, you can then use a module bundler such as Browserify, webpack or rollup.js.

ES5/ES6

This function targets ES5, but as of Locutus 2.0.2 we also support ES6 functions. Locutus transpiles to ES5 before publishing to npm.

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.

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we don't consider it to be a bad thing that many of our functions are first iterations, which may still have their fair share of issues. We hope that these flaws will inspire others to come up with better ideas.

This way of working also means that we don't offer any production guarantees, and recommend to use Locutus inspiration and learning purposes only.

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

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.

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

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