How to exclude a whole word including an escaped character from a search?

Instead of matching the slashes to split you could also use the "reverse" regex to find all the matches.

const string = "PHP/JAVA/TCP/IP/PYTHON/JAVASCRIPT";
const regex = /(TCP\/IP)(?=\/|$)|[^/]+/g;
//             ^       ^
// The group is unnecessary here, but is required in my second example.

console.log(string.match(regex));

If you've more exceptions you can make this dynamic by doing the following:

const string = "PHP/JAVA/TCP/IP/PYTHON/JAVASCRIPT/AB/CDE/FOO/UDP/TCP/AB/CD";
const exceptions = ["TCP/IP", "AB/CD", "AB/CDE", "UDP/TCP"];

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#Escaping
function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
}

let pattern = exceptions.map(escapeRegExp).join('|');
    pattern = `(${pattern})(?=/|$)|[^/]+`;
const regex = new RegExp(pattern, "g");

console.log(string.match(regex));

Let me give you a short rundown of what this does.

1. First escape all regex special characters inside the exceptions array.
2. Join them together with the | character (regex OR).
3. Now for the regex itself. Match one of the exceptions. The match must be followed by either an / character or the end of the string ($). If none of the the exceptions match, check if the character is a non-/. If this is the case match as many non-/ as possible.

Note: If you for some reason have the exceptions A/B and A/B/C, you should rearrange the array so that A/B/C comes before A/B. If this is not done you get the matches ["A/B", "C"] for the string "A/B/C" due to the fact that the A/B is indeed followed by a forward slash. Sorting the array based on string length (largest first) resolves this.

No The "negative lookbehind" feature may not be supported in all browsers. warning.

const string = 'PHP/JAVA/TCP/IP/PYTHON/JAVASCRIPT/ABC/ABDEFIP';
const regex = /\/(?![^TCP]*IP)/g;
const output = string.replace(regex, ' ');

console.log(output);

As negative lookbehinds are not fully supported, you might match what you do not want and capture what you do want in a capturing group.

Your values are in the first capturing group $1

\bTCP\/IP\b|(\/)

That will match:

• \bTCP\/IP\b Match TCP/IP between word boundaries
• |
• (!\/) capture a forward slash in group 1

See a regex demo

I was able to use Regexr to build a Regex that matched what I believe you're asking - every / that does not exist within TCP/IP.

I had to split your lookaround into a negative lookbehind for TCP ((?<!TCP)) then the / (\/) then a negative lookahead for IP ((?!IP))

The resulting Regex is (?<!TCP)\/(?!IP)

See: https://regexr.com/4fccb

I could not figure out a way to do this with pure regex, but an alternative to regex would be to just split on /, and then iterate the resulting array once to handle the edge case of a TCP/IP entry:

var input = "PHP/JAVA/TCP/IP/PYTHON/JAVASCRIPT"
var parts = input.split("/")
var keep = [];
var flag = false;
for (var i = 0; i < parts.length; i++) {
    if (parts[i] == "TCP") {
        flag = true;
        keep.push(parts[i]);
        continue;
    }
    else if (parts[i] == "IP" && flag) {
        keep.pop();
        keep.push("TCP/IP");
    }
    else {
        keep.push(parts[i]);
    }
    flag = false;
}

console.log(keep);