How to retrieve data-bind attribute value in html document

You can do it with a regular expression:

const img = document.querySelector('img');
const bind = img.getAttribute('data-bind');
const regex = /(http|ftp|https):\/\/([\w_-]+(?:(?:\.[\w_-]+)+))([\w.,@?^=%&:/~+#-]*[\w@?^=%&/~+#-])?/;

if (regex.test(bind)) {
  const url = regex.exec(bind)[0];
  console.info(url);
}

<img data-bind="attr: {src: app.utils.getFavicon('http://gamovideo.com/9tbtyuoti8ae')}" src="http://www.google.com/s2/favicons?domain=gamovideo.com"/>

If regular expressions scare you, here is an example of how to make it simpler but equally functional;))

$(function (){
 url = $("img").data("bind").split("'")[1];
 console.log(url);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<img data-bind="attr: {src: app.utils.getFavicon('http://gamovideo.com/9tbtyuoti8ae')}" src="http://www.google.com/s2/favicons?domain=gamovideo.com"/>

In the example I use jQuery because it's easy to use, cross-platform and lets you develop more by writing less.

Now I explain: the Method split divides a string of characters in an array using a character (or string) as a separator, in the case that you think it would be:

String to be converted:

attr: {src: app.utils.getFavicon('http://gamovideo.com/9tbtyuoti8ae')}" src="http:
//www.google.com/s2/favicons?domain=gamovideo.com

String (or Character) used as separate (or delimiter): '

Matrix created in the process of division:

0:attr: {src: app.utils.getFavicon(
1:http://gamovideo.com/9tbtyuoti8ae
2:)}" src="http://www.google.com/s2/favicons?domain=gamovideo.com

That's why when we execute: $("img").data("bind").split("'")[1] , it returns index 1 of the matrix which is in this case the url: 1:http://gamovideo.com/9tbtyuoti8ae .

I hope this serves you, Greetings !! ;))