Regexp to replace string

Question

I have below string pattern like Below.

"XX0XX XX7XX XX11XX XX26XX XX30XX XX38XX XX45XX **3** 10.1, Belkin Keyboard Folio"

I have to replace last "3" with "XX49XX" which does not have prefix and suffix with "XX"

I have done below code so far which is replacing first occurrence of 3 which is not correct

var string = 'XX0XX XX7XX XX11XX XX26XX XX30XX XX38XX XX45XX 3 10.1, Belkin Keyboard Folio';

str = string.replace(/3/, 'XX49XX');

You need to edit your question to make it clear exactly what is your input, your desired output and what you have tried so far. — Tom Fenech
– Tom Fenech, Commented May 23, 2014 at 10:07
I have below string pattern I have to replace last "3" which does not have prefix and suffix XX var string = 'XX0XX XX7XX XX11XX XX26XX XX30XX XX38XX XX45XX 3 10.1, Belkin Keyboard Folio'; str = string.replace(/3/, '49'); — user1046987
– user1046987, Commented May 23, 2014 at 10:09
There is an "edit" link under your question, you should use that. — Tom Fenech
– Tom Fenech, Commented May 23, 2014 at 10:11

anubhava · Accepted Answer · 2014-05-23 10:29:46Z

2

You can use use negative lookahead to match last 3:

string = string.replace(/3(?!.*3)/, 'XX49XX');

// XX0XX XX7XX XX11XX XX26XX XX30XX XX38XX XX45XX 49 10.1, Belkin Keyboard Folio

answered May 23, 2014 at 10:14

anubhava

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Comments

Niet the Dark Absol · Accepted Answer · 2014-05-23 10:23:54Z

0

While JS sadly doesn't have the capacity for lookbehinds, you can use a lookahead:

string.replace(/3(?!\d*XX)/, "XX49XX");

This will ensure that the 3 that you get is not part of a XX##XX structure.

answered May 23, 2014 at 10:23

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Taemyr · Accepted Answer · 2014-05-23 10:27:25Z

0

anubhave shows how to match the last occurence of the digit 3.

You can also match to the relevant part of the string.

string.replace(/\b\d+ (\d+\.\d+, Belkin Keyboard Folio)/, 'XX49XX')

This replaces the first number (one or more digits) in the substring with the form <number> <number>.<number>,Belkin Keyboard Folio

answered May 23, 2014 at 10:21

Taemyr

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