Add commas or spaces to group every three digits

Question

I have a function to add commas to numbers:

function commafy( num ) {
  num.toString().replace( /\\B(?=(?:\\d{3})+)$/g, \",\" );
}

Unfortun

Answer 1

Assuming your usage examples are not representative of already-working code but instead desired behavior, and you are looking for help with the algorithm, I think you are already on the right track with splitting on any decimals.

Once split, apply the existing regex to the left side, a similiar regex adding the spaces instead of commas to the right, and then rejoin the the two into a single string before returning.

Unless, of course, there are other considerations or I have misunderstood your question.