best-matched-rx.md

/*
 * to ilustrate it better, the idea is that the user will pass
 * two regex(so, they are dynamic).
 * I want to see if there is a way in which we can find out which
 * dynamic rx fits better the requirements
 */

let rx = [
      /.+\/images\/.+/i,
      /.+\/images\/one-specific-image.png/i
    ];

function match(str){
    rx.forEach(function(currentRX){
        if(str.match(currentRX)){
            return currentRX;
        }
    });
}

// should return the first rx
match("domain.com/images/something.png");
// should return the second rx, but matches the first rx first
match("domain.com/images/one-specific-image.png");

I was thinking on using the "length" of the rx, but it is not the best option. The most interesting way would be to find out the most complex one. It would be really useful to figure out the "complexity" of each regular expression.

You could order the regexes in order of complexity, filter thru them and pop off the last one - assuming that is the most "complex" ala:

 let rx = [
      /.+\/images\/.+/i,
      /.+\/images\/one-specific-image.png/i
    ];

function match(str){
    return rx.filter((currentRX) => {
        if(str.match(currentRX)){
            return currentRX;
        }
    }).pop();
}

I just re-read your post. The "user" will pass in the regexes, so how do you presume to know if they will follow ordering protocol? So, I guess you could sort the regex on "length" and we can presume that the longest is the most complex? OR we can run thru all the regexes, attach a timestamp, and grab the greatest (assuming greatest would be longest, which would mean "more complex"?).

If you use a group for the thing that varies, this solution might work:
https://jsbin.com/vewesabipo/edit?js,console

Using the processing time or the length, as proposed by @dsacramone would work, but I am not sure they would be 100% reliable!
I was thinking on comparing the number of groups, indeed, and I believe that will do it!
I believe the solution from @BrenoC makes total sense! I will create a bunch of unit tests so we can assure it will be fully reliable!
:)

I'm interested in the results! Please, share if you can!

@BrenoC I added it to the DSW project, here https://github.com/NascHQ/dsw/
The project is focused on helping developers to create and use service workers and develop their offline web apps.
The module is this one: https://github.com/NascHQ/dsw/blob/development/src/best-matching-rx.js

Feel free to contribute :)