Add a hook or event to all AJAX requests on a page

(function() {
            var origOpen = XMLHttpRequest.prototype.open;
            XMLHttpRequest.prototype.open = function() {
                console.log('request started!');
                this.addEventListener('load', function() {
                    console.log('request completed!');
                    // console.log(this)
                    //console.log(this._url)
                    //console.log(this.status)
                });
                origOpen.apply(this, arguments);
            };
        })();

This code will listen to all the XHR, fetch, and ajax requests and you can attach your functions on request start or on request status 200.