RegExp search within part of string
Since the javascript RegExp object does not offer any in-built substring capabilities and javascript does not allow any pointer magic you have no choice but to use substring. However, unless you are expecting gigantic strings I wouldn’t worry too much substring’s performance. Substring is basically a memory copy which is an incredibly optimized operation at the hardware level (think L1-3 caches, cpu extensions that allow copying 128 bits per clock cycle, etc).
Just for my amusement I offer some creative alternatives to substring:
-
Keep your lastIndex trick, but add `.{m, n}$’ to the end of your regex:
- let
m
bestr.length - endIndex
. - and let
n
bestr.length - lastIndex
- let
-
use a regex engine written in javascript that has in-built substring scanning.
-
submit an rfc to Ecma International.
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