Intercept any ajax request

intercept_ajax.js

(function(open) {
    XMLHttpRequest.prototype.open = function(method, URL, async, user, password) {
        if (URL.indexOf("xxxx") > -1) {
            // console.log(method, URL, async, user, password);
            this.addEventListener('readystatechange', function () {
                if(this.responseText !== '' && this.readyState == 4) {
                    var oldResponseText = this.responseText;
                    // ...
                    var newResponseText = 'blabla';
                    Object.defineProperty(this, 'responseText', {
                        get: function() { return newResponseText; },
                    });
                }
            }, false);
        }
        open.call(this, method, URL, async, user, password);
    };
})(XMLHttpRequest.prototype.open);