Split the string from backward

Question

I want to split string into array with fix number of char but the counting should be from backwards. In the following example I want to split the string into array with set of 3 char:

InputString = '1234567'

Wanted:

OutputArray= [1,234,567]

Tried:

InputString.match(/.{1,3}/g)
OutputArray = [123,456,7]

Answer 1

Use String#match with positive lookahead assertion regex.

var InputString = '1234567';

console.log(
  InputString.match(/\d{1,3}(?=(\d{3})*$)/g)
)

Regex explanation here.

---

With String#split method with positive lookahead assertion for asserting position to split.

var InputString = '1234567';

console.log(
  InputString.split(/(?=(?:\d{3})+$)/)
)

Regex explanation here.