javascript regex match anything not inside a specific attribute

Question

Lets say I want to match urls, which are not inside a specific set of attributes in html tags.

<span cstm1="url1" cstm2="url2" data-x="url3">url4</span>

I want to match url3 and url4 only, so I tried something like:

/(?!(?:cstm1|cstm2)=["']?)(url_regex)/g

problem is that the negative look ahead assertion need something before it and I cannot ensure that the number cannot be inside quotes because it'll still be valid, so I don't have anything reasonable to put behind this negative look ahead assertion.

If I was able to use negative look behind assertion it'll be really easy, but I'm using javascript which doesn't support it, so I'm kinda stuck and looking for help on how to achieve this.

I look for regex only solution.

EDIT:

The url regex I used to find urls:

((?:(?:https?):\/\/)(?:\S+(?::\S*)?@)?(?:(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|\[(?:(?:[0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|(?:[0-9a-fA-F]{1,4}:){1,7}:|(?:[0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|(?:[0-9a-fA-F]{1,4}:){1,5}(?::[0-9a-fA-F]{1,4}){1,2}|(?:[0-9a-fA-F]{1,4}:){1,4}(?::[0-9a-fA-F]{1,4}){1,3}|(?:[0-9a-fA-F]{1,4}:){1,3}(?::[0-9a-fA-F]{1,4}){1,4}|(?:[0-9a-fA-F]{1,4}:){1,2}(?::[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:(?:(?::[0-9a-fA-F]{1,4}){1,6})|:(?:(?::[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(?::[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(?:ffff(?::0{1,4}){0,1}:){0,1}(?:(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9]).){3,3}(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9])|(?:[0-9a-fA-F]{1,4}:){1,4}:(?:(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9]).){3,3}(?:25[0-5]|(?:2[0-4]|1{0,1}[0-9]){0,1}[0-9]))\]|localhost|(?:xn--[a-z0-9\-]{1,59}|(?:(?:[a-z\u00a1-\uffff0-9]+-?){0,62}[a-z\u00a1-\uffff0-9]{1,63}))(?:\.(?:xn--[a-z0-9\-]{1,59}|(?:[a-z\u00a1-\uffff0-9]+-?){0,62}[a-z\u00a1-\uffff0-9]{1,63}))*(?:\.(?:xn--[a-z0-9\-]{1,59}|(?:[a-z\u00a1-\uffff]{2,63}))))(?::\d{2,5})?(?:\/[^"'()<>\s]*)?)

Answer 1

In the absence of lookbehind you can use capture group to extract your results.

/(?:cstm1|cstm2)=(['"]?)\d+\1|(\b\d+\b)/ig

Use captured group #2 for your matches.

RegEx Demo