PHP's array_reverse in JavaScript

How to use

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

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	array_reverse( [ 'php', '4.0', ['green', 'red'] ], true)	{ 2: ['green', 'red'], 1: '4.0', 0: 'php'}

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.

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

module.exports = function array_reverse(array, preserveKeys) {
  //  discuss at: https://locutus.io/php/array_reverse/
  // original by: Kevin van Zonneveld (https://kvz.io)
  // improved by: Karol Kowalski
  //   example 1: array_reverse( [ 'php', '4.0', ['green', 'red'] ], true)
  //   returns 1: { 2: ['green', 'red'], 1: '4.0', 0: 'php'}

  const isArray = Object.prototype.toString.call(array) === '[object Array]'
  const tmpArr = preserveKeys ? {} : []
  let key

  if (isArray && !preserveKeys) {
    return array.slice(0).reverse()
  }

  if (preserveKeys) {
    const keys = []
    for (key in array) {
      keys.push(key)
    }

    let i = keys.length
    while (i--) {
      key = keys[i]
      // @todo: don't rely on browsers keeping keys in insertion order
      // it's implementation specific
      // eg. the result will differ from expected in Google Chrome
      tmpArr[key] = array[key]
    }
  } else {
    for (key in array) {
      tmpArr.unshift(array[key])
    }
  }

  return tmpArr
}

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.

Now go and: [ View on GitHub | Edit on GitHub | View Raw ]

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