you can use ? at end of group for optional group patterns:

its work fine: /(<imgs)[^>]*(src=S+)[^>]*(salt=["|'].*?["|'])?[^>]*(/?>)/gm

and here the live link you can check demo: https://regex101.com/r/u2uWGX/1

If you have a set of img elements in your HTML. You can also get the src and alt value by looping a HTMLCollection.

Demo :

const imgCollection = document.getElementsByTagName('img');

for (let item of imgCollection) {
  console.log('src :', item.src)
  console.log('alt :', item.alt)
}

<img src="https://example.com/image" alt="example1">
<img src="https://example.com/image">

I need to get from all the images the src and alt of the html code. I managed to get it but I have the following problem:

• If the image has no alt, it does not detect me the image. In these cases I need to get only the src.

The following code works with problem:
https://regex101.com/r/3Vlkql/1

(<imgs)[^>]*(src=S+)[^>]*(salt=["|'].*?["|'])[^>]*(/?>)

Substitution:

$1$2$3$4

Result:

<img src="https://example.com/image" alt="example1">

Problem: My regex only detect if have src and alt. But if not have alt, the regex not detect me. How can I do with regex to get both?

This not match with regex:

<img src="https://example.com/image">

• src & alt
• only src

I dont have problem if i need to use 2 regex to get my purpose.