Userscript for showing GrubHub delivery fees in search results

script.js

// ==UserScript==
// @name         Show Grubhub Delivery Fees
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Why on earth do I have to do this? I hate you.
// @author       You
// @match        https://www.grubhub.com/search*
// @grant        none
// ==/UserScript==

let oldXHROpen = window.XMLHttpRequest.prototype.open;
window.XMLHttpRequest.prototype.open = function(XMLHttpRequest) {
    var self = this;
    this.addEventListener("readystatechange", function() {
        if (!this.readyState === 4) {
            return;
        }
    	if (this.responseURL.indexOf('search') == -1) {
    		return;
    	}


        // fix up some slight inconsistencies in data format on first and subsequent loads
    	var d = JSON.parse(this.responseText);
        if (!d) {
            return;
        }
        if (d.search_result) {
            d = {
                results: d.search_result.results,
                sponsored_result: d.sponsored_result
            };
        }
    	if (!d.results) {
    		return;
    	}

    	var allResults = d.results;
    	if (d.sponsored_result && d.sponsored_result.results) {
    		allResults = allResults.concat(d.sponsored_result.results);
    	}

        if (allResults.length < 1) {
            return;
        }

        // Results for previous orders and stuff are showing up at this point.
        // Get rid of them.
        if (!allResults[0].restaurant_id) {
            return;
        }

    	// Set up an interval to occasionally check to see if we can populate the
        // new data yet, and then do so.
        (function() {
            var updater = setInterval(function(d) {
                if (!document.querySelector('#' + CSS.escape(d[0].restaurant_id))) {
                    return;
                }

                function formatPrice(pennies) {
                    return '$' + (parseInt(pennies) / 100.0).toFixed(2);
                }

                for (var i = 0; i < d.length; i++) {
                    var anchor = document.querySelector('#' + CSS.escape(d[i].restaurant_id));
                    if (!anchor) {
                        return;
                    }
                    var sibling = anchor.nextSibling;
                    var deliveryMin = sibling.querySelector('ghs-restaurant-delivery-min');
                    var deliveryPrice = deliveryMin.querySelector('.deliveryPrice');
                    if (!deliveryPrice) {
                        deliveryPrice = document.createElement('p')
                        deliveryPrice.textContent = 'Fee: ' + formatPrice(d[i].delivery_fee.price);
                        deliveryPrice.className = 'deliveryPrice';
                        deliveryMin.appendChild(deliveryPrice);
                    } else {
                        deliveryPrice.textContent = 'Fee: ' + formatPrice(d[i].delivery_fee.price);
                    }

                    if (d[i].delivery_fee.price <= 200) {
                        deliveryPrice.style.color = '#0e7c28';
                    } else if (d[i].delivery_fee.price <= 350) {
                        deliveryPrice.style.color = 'black';
                    } else {
                        deliveryPrice.style.color = '#ff8080';
                    }
                }

                clearInterval(updater);

            }, 200, allResults);
        })(allResults);
    }, false);
    oldXHROpen.apply(this, arguments);
};