JSFiddle - React, Tailwind, and code Playground

HTML

<div id="log"></div>

JavaScript

var re = /\[([a-f0-9]{8}(?:-[a-f0-9]{4}){3}-[a-f0-9]{12})\]/i;

// finds first occurrence of a GUID within square brackets in a string
function extractGuid(value) {    
    
    // the RegEx will match the first occurrence of the pattern
    var match = re.exec(value);
    
    // result is an array containing:
    // [0] the entire string that was matched by our RegEx
    // [1] the first (only) group within our match, specified by the
    // () within our pattern, which contains the GUID value
    return match ? match[1] : null;
}
function test(value) {
    var guid = extractGuid(value);
    var msg;
    if(guid ) {
        msg = 'Guid found within ' + value+ ': ' + guid;       
    } else {
        msg = 'Guid not found within ' + value;
    }
    $('#log').append(msg + '<br/><br/>');
}
test('AccommPropertySearchModel.AccommPropertySearchRooms[6a2e6a9c-3533-4c43-8aa4-0b1efd23ba04].ADTCount');
test('AccommPropertySearchModel.AccommPropertySearchRooms[6a2e6a9c-3533-4c43-8aa4-0b1efd23ba04].ADTCount');
test('AccommPropertySearchModel.AccommPropertySearchRooms[6A2E6A9C-3533-4C43-8AA4-0B1EfD23BA04].ADTCount');
test('AccommPropertySearchModel.AccommPropertySearchRooms.6A2E6A9C-3533-4C43-8AA4-0B1EfD23BA04.ADTCount');
test('AccommPropertySearchModel.AccommPropertySearchRooms.ADTCount');