[OJFord]

The words for the orders of magnitude don't group by thousand like in English (*thousand, million, billion, and so on) but by thousand (hazaar), hundred thousand (lakh), ten million (crore), and I don't know what next.

So the comma separation reflects the words, as in English.

> 38,625

38 hazaar ... Vs. 38 thousand ...

> 13,38,625 vs. 1,338,625

13 lakh ... Vs. 1.3 million ...

> 1,00,13,38,625 vs. 1,001,338,625

100 crore Vs. 1.0 billion

This would no doubt be an entry in a hypothetical 'falsehoods programmers believe about numbers'! I.e. use things like Intl.NumberFormat in the browser, rather than home-grown 'group 3 digits and insert a comma then join again'.

(* yes, I'm going to conveniently ignore 'hundred' and its occasional/domain use like 'twelve hundred'.)

[oblio]

> The words for the orders of magnitude don't group by thousand like in English

It's not only in English, as far as I know it's almost everywhere else, the entire Western world plus its former colonies and I think even places like China.

The Indian subcontinent is the exception.

[taejo]

Chinese uses powers of ten thousand, I believe, but I don't know if that's reflected in the way numerals are written.

[wtmt]

> use things like Intl.NumberFormat in the browser, rather than home-grown 'group 3 digits and insert a comma then join again'.

That home grown solution wouldn’t work in many western countries either, where comma is a decimal separator and dot/period is the thousands separator.

[OJFord]

Yep, true. But don't be tempted just to iterate on it to take account of that and whatever you discover next!

[hiyer]

We have Arab after Crore, but it's not commonly used. We just say 1000 crore or 1 lakh crore, etc.