CODEWITHSUNDEEP
regex
seanjacob
seanjacob

Reputation: 2258

What does +(?!\d) in regex mean?

I have also seen it as +$.

I am using

$(this).text( $(this).text().replace(/(\d)(?=(\d{3})+(?!\d))/g, "$1,") );

To convert 10000 into 10,000 etc.

I think I understand everything else:

Upvotes: 5

Views: 4410

Answers (2)

Asherah
Asherah

Reputation: 19347

I think you're slightly misreading it:

  • (?=\d{3}) - if followed by 3 numbers

Note that the regexp is actually:

(?=(\d{3})+

i.e. you've missed an open paren. The entire of the following:

(\d{3})+(?!\d)

is within the (?= ... ), which is a zero-width lookahead assertion—a nice way of saying that the stuff within should follow what we've matched so far, but we don't actually consume it.

The (?!\d) says that a \d (i.e. number) should not follow, so in total:

  • (\d) find and capture a number.
  • (?=(\d{3})+(?!\d)) assert that one or more groups of three digits should follow, but they should not have yet another digit following them all.

We replace with "$1,", i.e. the first number captured and a comma.

As a result, we place commas after digits which have multiples of three digits following, which is a nice way to say we add commas as thousand separators!

Upvotes: 7

M Abbas
M Abbas

Reputation: 6479

?! means Negative lookahead , it is used to match something not followed by something else, in your case a digit

Upvotes: 1

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