How to convert Persian and Arabic digits of a string to English using JavaScript?

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Oneliner of all 6 possible translations between English, Arabic, and persian Digits.

const e2p = s => s.replace(/\d/g, d => '۰۱۲۳۴۵۶۷۸۹'[d])
const e2a = s => s.replace(/\d/g, d => '٠١٢٣٤٥٦٧٨٩'[d])

const p2e = s => s.replace(/[۰-۹]/g, d => '۰۱۲۳۴۵۶۷۸۹'.indexOf(d))
const a2e = s => s.replace(/[٠-٩]/g, d => '٠١٢٣٤٥٦٧٨٩'.indexOf(d))

const p2a = s => s.replace(/[۰-۹]/g, d => '٠١٢٣٤٥٦٧٨٩'['۰۱۲۳۴۵۶۷۸۹'.indexOf(d)])
const a2p = s => s.replace(/[٠-٩]/g, d => '۰۱۲۳۴۵۶۷۸۹'['٠١٢٣٤٥٦٧٨٩'.indexOf(d)])

e2p("asdf1234") // asdf۱۲۳۴
e2a("asdf1234") // asdf١٢٣٤
p2e("asdf۱۲۳۴") // asdf1234
a2e("asdf١٢٣٤") // asdf1234
p2a("asdf۱۲۳۴") // asdf١٢٣٤
a2p("asdf١٢٣٤") // asdf۱۲۳۴

Explaination:

  • (s => f(s))(x) is a lambda function that is immediately executed, and will be equal to f(x)
  • s.replace(pattern, function) looks for matches of pattern in s, for every match m it will replace m with function(m) in the string.
  • /\d/g is a regex pattern, \d means a digit in the English language, g means global. If you don’t specify the g it will only match the first occurrence, otherwise it will match all the occurrences.
  • In this case for every English digit d in the string, that digit will be replaced by '۰۱۲۳۴۵۶۷۸۹'[d] so, 3 will be replaced by the third index in that list('۰۱۲۳۴۵۶۷۸۹') which is ‘۳’
  • /[۰-۹]/g is the equivalent regex for Persian digits this time we can’t use the same method, before we took advantage of the fact that javascript is dynamically typed and that d is automatically converted from a string(regex match) to a number(array index) (you can do '1234'['1'] in javascript which is the same as '1234'[1])
  • but this time we can’t do that because '1234'['۱'] is invalid. so we use a trick here and use indexOf which is a function that tells us the index of an element in an array(here a character in a string) so, '۰۱۲۳۴۵۶۷۸۹'.indexOf(۳) will give us 3 because '۳' is the third index in the string '۰۱۲۳۴۵۶۷۸۹'

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