Really useful page for generating regexes of ip ranges. Note they are missing some parenthesis in places though.

Actually, it'd be better to express this as /^10.\d{4,9}/[-._;()/:a-zA-Z0-9]+$i (adding lowercase letters a-z, instead of using the case insensitivity flag "i") to avoid compatibility issues with certain regex parsers

cool, it will show how many steps are needed to performce the regex! Greatful for tuning regex for performance

Regex kontrolü https://regex101.com/

so greedy is evil? since it'll backtrack form the end!

but in log analysis field, almost every line are machted, we'just want to use regex to extract fields inside the line. Is the "the longer the better" still matter?

Interesting dive into how string slicing with String#substring is implemented in the Dart and V8 VMs and the performance consequences of that. This investigation was prompted by poor performance of a port of less.js lexer to Dart vs. the original JS implementation.

The article ends with benchmarks showing the cost of trying to match sequences of characters in a lexer using a regex vs. manually.

Neat trick for matching regular expressions within a string starting at a fixed position using pre-ES6 features:

1. Create a regex with the global flag set which matches pattern|() where () is an irrefutable pattern which is guaranteed to match
2. Set regex.lastIndex to the position you want to match at
3. Use regex.exec(str)

Notes on how to match a regex starting at a given position in a string, making use of the sticky flag introduced in ES6.