Is there a way to verify if a capturing group has been involved in the regex or not?

Question

Is there a way to verify if a capturing group has been involved in the regex or not?

Looking to extract website URLs from text and have a regex in place so far.

((http|https):\/\/)?(www\.)[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%_\+.~#?&//=]*)

Issue:

If www. is made optional, the regex ends up detecting strings like vue.js or something.ts as URLs and even identifies emails as web URLs. If www. is made mandatory, it fails to detect URLs like this.

The current regex works well for my requirements if I can enhance its flexibility to capture the mentioned URLs.

Query:

I aim to ascertain if the capture group containing http or https has been included in the regex. If the URL includes http, then make www. optional; otherwise, make it mandatory.

Any thoughts on potential solutions to address this challenge?

javascript regex typescript

Answer 1

Answer №1

If my understanding is correct, you are looking to not accept "example.com".

You can make it mandatory for either the "http" (s) or the "www" part to be included in the URL. This way, it becomes a requirement rather than an option. If both are provided, the "www." part will already be matched by the regular expression without any additional considerations needed.

It's worth noting that http|https can be simplified to https?.

Below is the regular expression along with some sample tests:

const re = /(https?:\/\/|www\.)[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%_\+.~#?&//=]*)/

const tests = [
    "http://www.example.com",
    "http://example.com",
    "www.example.com",
    "example.com",
]


for (let url of tests) {
    console.log(re.test(url), url);
}

Answer 2

If my understanding is correct, you are looking to not accept "example.com".

You can make it mandatory for either the "http" (s) or the "www" part to be included in the URL. This way, it becomes a requirement rather than an option. If both are provided, the "www." part will already be matched by the regular expression without any additional considerations needed.

It's worth noting that http|https can be simplified to https?.

Below is the regular expression along with some sample tests:

const re = /(https?:\/\/|www\.)[-a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%_\+.~#?&//=]*)/

const tests = [
    "http://www.example.com",
    "http://example.com",
    "www.example.com",
    "example.com",
]


for (let url of tests) {
    console.log(re.test(url), url);
}

Is there a way to verify if a capturing group has been involved in the regex or not?

Answer №1

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