Randexp.js: Create random strings that match a given regular expression

I've made a node package that does the same thing, a few years ago: https://github.com/arcanis/pxeger

I mainly used it to generate test mail addresses. For example, the following will generate 36 test email addresses:

    (blue|red|yellow|green).(oak|cedar|willow)@(yahoo.co.uk|google.com|example.org)

Exrex does the same in Python and much more:

   - Generating all matching strings
   - Generating a random matching string
   - Counting the number of matching strings
   - Simplification of regular expressions

https://github.com/asciimoo/exrex (AGPL licensed)

It's practical, if you check the new one is not a duplicate - the lib info does not state how distinct the values would be, or how does it uses the RNG.

Depending on what you really need (output string format, amount of numbers, non-additive links), you should find a hash function for your fit. You can always start by looking for youtube url hash.

I'd be surprised if it had the amount of entropy you need. I haven't looked at the source, but javascript in a browser is not a good source of random numbers.

Safari loved that.

Testing.

Offhand, I think it could be useful for ensuring your regex is doing what you want it to do. Perhaps I'd write a regex to validate a xxx-xxx-xxxx telephone number:

    \d{3}\-\d{3}\-\d{3}

Oops! I made a typo! That last 3 should be a 4. If I were tired, I could very easily see myself doing something like this. If I could put it into a tool and see 100 things which match it, I'd see very quickly that I messed something up.

According to the readme:

"Regular expressions are used in every language, every programmer is familiar with them. Regex can be used to easily express complex strings. What better way to generate a random string than with a tool you can easily use to express the string any way you want?"

An example where this is useful (I guess) is generating data for tests. You can easily define an email regexp to generate random "valid" values for each model.