How can I get an output out of a regular expression in JavaScript?

Question

I am trying to create a very simple engine that will generate some random data based on a token.
I was thinking that the input for the engine can be regex expressions so for example

engine will get [0-9] will yield any random number like 9 9999 0897 000
engine will get \w    will yield any random word (even without meaning) like asdd gwasss ttt were khhu encyclopedia 

so if I want a random email, I will write an expression:

  \w@\w.com

for example random phone number

\d{3}-\d{3}-\d{4}

I am not sure how to approach this, Is there any JS library I can use to parse regex and override to get the output the way I want it? Or do I need to write my own parser?

pseudo code:

 function getRandom('\d{3}-\d{3}-\d{4}'); 

will return

   384-495-3344  or 433-244-3454   etc

Answer 1

Consider using an existing Regular Expression parser which outputs an AST .

For example for JavaScript:
https://www.npmjs.com/package/regjsparser
https://github.com/jviereck/regjsparser

The demo page here allows you to see the generated AST:
http://www.julianviereck.de/regjsparser/

Then you could look through the "type" in the AST, in this case this includes the "dot" type:

    {
      "type": "dot",
      "range": [
        4,
        5
      ],
      "raw": "."
    },

Also note there is a JS library to generate regular expressions from the AST:
https://www.npmjs.com/package/regjsgen
https://github.com/bnjmnt4n/regjsgen

PS: I posted a similar answer to this for a different problem here https://stackoverflow.com/a/57096632/406712 it might be worth a look.