A regex cheatsheet for all those regex haters (and lovers) πŸ‘€

Catherine πŸ‘©πŸ»β€πŸ’» on January 10, 2019

My experience with regex I have always stayed far away from regex. In one of my first year computer science labs, there was an exercise ... [Read Full]
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I would like to share my two favorites tools to create, edit, visualize and debug regex:

  • Debuggex.com
    my favorite tool, it can make a diagram of how your regex will work, you can add multiple lines to test if the regex match the strings that you expect and also has a cheatsheet

  • RegExr.com
    Similar to debuggex except it doesnt generate the diagram, but in my opinion their cheatsheet is cleaner and easier to find what you need.


Hey @catherinecodes , I think you've missed the greedy vs lazy matching:

// greedy
/".+"/.exec('a "witch" and her "broom" is one') // "witch" and her "broom"
// lazy
/".+?"/.exec('a "witch" and her "broom" is one') // "witch"

Nice! I didn't learn those yet


You can achieve laziness with negated set too:

/"[^"]+"/.exec('a "witch" and her "broom" is one') // "witch"

Just to nitpick, the second wildcard example should be .*, and your group examples will fail because you didn't capture a space (it is ice cold outside and it isΒ Β cold outside match but not it is cold outside)

Regex is great! And not at all as hard as it looks. Although I still don't have the hang of lookahead/lookbehinds yet πŸ˜…


Good catch Ryan! Thank you! I've updated the cheatsheet ☺️

I still need some more practice as well πŸ˜…lookaheads and lookbehinds were totally new to me! I didn't know about them during my CS lab 😲


You should add a note about lookbehind compatibility. It's not available in all browsers quite yet.



Very nice and brainstorming regex challenge is RegexGolf - alf.nu/RegexGolf :)

Another view on "regex games" is Regex Crosswords. Very nice idea. regexcrossword.com/


These look fun! Thanks for sharing :)


I am going to bookmark the Gist version of your very wonderful cheat sheet. I look forward to using it every time I work with regex. The samples appear in a very logical progression that makes it very easy to understand and use. Thank you!


So happy you find it useful!!! ☺️☺️☺️


If you are adding usefull regex functions at the end of the code, you could also add information on replace function taking a callback as an argument.

const p = 'The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?';
p.replace('dog', (match, matchIndex, originalString) =>{
return match+"test"+matchIndex // match based replacer


Regex = Black Magic
Convince me if not! Never sure why something works. I just don't touch it and put the script inside as many as folders possible in case some evil spirit leaks out to our world.


Hide it away!!! πŸ˜‚πŸ˜‚πŸ˜‚


Another really great resource is regular-expressions.info/


Nice post! I recommend this site too: regex101.com/


Great post, Catherine. πŸ‘πŸΌπŸ‘πŸΌ

Created a gist out of this post. 😊

Link to Gist


Thank you Sarthak! I'll link it in the post :)


Totally saving this, as I'm supposed to be learning regex next week in class!


In the β€˜wildcards’ example, you’ve written

regex = /h.llo/; // the "" matches any character(s) zero or more times... matches
"hello", "heeeeeello", "hllo", "hwarwareallo"

How does it match "hwarwareallo" ? Does not the β€œ.” indicate only one character?


Another recommendation (not free though): Regular Expressions Cookbook


Love this. I wish more people would take advantage of regex, it's so powerful! I love using regex101.com since it does a great job of explaining your regex as you write it out.


+1 to regexr.com

Great site... but now you have two problems.


Awesome! I also translated one Chinese copy: gist.github.com/cxa/901e1862cd9ddf...


Hi, useful post!
Another online regex tester: extendsclass.com/regex-tester.html


I'm new to RegEx so thank you very much for taking the time to make this its a big help!


not free, but RegexBuddy is awesome

that alone helped me to love regexs and made it super easy to deal with complex expressions


This is excellent, thank you! I hope you don't mind, I added it (with credit) to the "Development" portion of my company's wiki for quick reference next time one of us has to use Regex!


I would add "how to reverse the sides of an equation" to this list. There are a few other handy tricks for coders, but this is the most common I can think of right now


Yes. If I understand you correctly, that would at the same time be a good example case for another detail I was about to suggest: Match-parenthesis references in the replacement.
Something like:
"a = b + c".replace(/^(.+?) *= *(.+)$/, "$2 = $1")


This is such an awesome article. thank you. There is also an article on regex for java developers. its awesome. dev.to/codechunker/introduction-to...


Sorry, but the terrible contrast with that black background makes this far too hard to read e.g. brown on black??


Here (techgeekbuzz.com/regex-cheat-sheet/) we have also listed a complete checklist of cheat sheet, Please check.

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