🦄 Lightweight reverse utility around strings, arrays, numbers and more.

$ npm install --save type-reverse

const reverse = require('type-reverse')

or...

import reverse from 'type-reverse'

Params

• input {String|Number|Array|Set}
• options {?Object}
• callback {?Function}
• returns {*}

reverse('pizza')
//=> azzip

Works with numbers too.

reverse(1234)
//=> 4321

When JavaScript's Array#reverse method is used, the original array is mutated, as in, the indexes of the elements are changed. On the other hand, this utility adopts the non-destructive array reversal method, which means the reverse() function doesn't mutate the array; it just returns the reversed array and still maintains the indexes of the elements in the original array.

const arr = [1, 2, 3]
arr.reverse() //=> [3, 2, 1]

Oops, we lost the indexes of elements in the initial array...

console.log(arr) //=> [3, 2, 1]

vs...

const arr = [1, 2, 3]
reverse(arr) //=> [3, 2, 1]

Yay! arr is not mutated. The indexes of its elements are still maintained...

console.log(arr) //=> [1, 2, 3]

If you've been wondering how to reverse Sets in JavaScript, here's it! The core reverse function can take in a Set as the input and then return the reversed Set...

const set = new Set([5, 4, 3, 4, 5])
reverse(set) //=> Set { 3, 4, 5 }

options is the second parameter to the function call and it is an object with two available properties. It can also take in a falsy value which would implicity get converted to an empty object.

This property defaults to index and applies to strings and numbers only.

reverse(/*...*/, {
  invert: '[index|word|sign]'
})

• index - interchanges the indexes of characters in the input...

  reverse(12345, { invert: 'index' }) //=> 54321
  reverse('of... unicorns', { invert: 'index' }) //=> snrocinu ...fo

• sign - inverts the sign in a number...

  reverse(1234, { invert: 'sign' }) //=> -1234

• word - swaps the location of words in a string...

  reverse('of... unicorns', { invert: 'word' }) //=> unicorns of...

This property defaults to true. It specifies whether to enforce preceding zeros in the result of a number that contains trailing zeros. See #3 for more info. Note that the result gets converted to a string. Disabling it would look like this...

reverse(240, { preserveZeros: false }) //=> 42

The callback takes in a function with two optional parameters that represent input and result respectively.

• input - the initial input that was passed into the function
• result - the output from reversing the input

const text = 'dog'

reverse(text, null, function(intitial, result) {
  return intitial + ' was changed to ' + result
}) //=> dog was changed to god

Did you just try to reverse a reaally huge number? Unfortunately, this utility doesn't support very large numbers. Trying to do so with this utility would throw a TypeError.

Olaolu Olawuyi

• github/whizkydee
• twitter/mrolaolu

MIT © Olaolu Olawuyi