inject.js

let lastUrl = null;
let interval = null;

const isDebug = true;

startInterval();

function debug(...values) {
    if (! isDebug) {
        return;
    }

    console.log(...values);
}

function startInterval() {
    debug('Starting interval');

    interval = setInterval(updateSaleHistory, 500);
}

function shouldRun() {
    return window.location.pathname.includes('property-for-sale')
        && document.location.href !== lastUrl;
}

function removeDivs() {
    document.querySelectorAll('.rm-sale-history').forEach(div => div.remove());
}

function updateSaleHistory() {    
    if (! shouldRun()) {
        return;
    }

    populate();
}

async function getDeliveryPointId(propertyId) {
    const url = 'https://www.rightmove.co.uk/properties/';
    const response = await fetch(url + propertyId);
    const data = await response.text();

    return data.match(/\"deliveryPointId\"\:([0-9]+)/)[1];
}

async function populate() {
    const results = document.querySelectorAll('.l-searchResult:not(.l-searchResult-loading)');
    const apiUrl = 'https://www.rightmove.co.uk/properties/api/soldProperty/transactionHistory/';
    
    if (results.length === 0) {
        debug('No results, skipping this time');
        return;
    }

    lastUrl = document.location.href;
    removeDivs();

    debug(`Fetching for ${results.length} search results`);
    
    debug('Interval stopping');
    clearInterval(interval);

    results.forEach(async result => {
        const propId = result.id.replace('property-', '');
        const currentPrice = result.querySelector('.propertyCard-priceValue').innerHTML;

        const deliveryPointId = await getDeliveryPointId(propId);

        const url = apiUrl + deliveryPointId;
        const target = result.querySelector('.propertyCard-price');

        const response = await fetch(url);
        const data = await response.json();

        debug(`Found ${data.soldPropertyTransactionHistories.length} transactions for propId ${propId}, pointId ${deliveryPointId}`);

        target.append(buildDiv(data.soldPropertyTransactionHistories, currentPrice));
    });

    startInterval();
}

function buildDiv(transactions, currentPrice) {
    let html = "No sale history";

    const div = document.createElement('div');
    div.className = "rm-sale-history";

    if (transactions.length > 0) {
        html = "<u><b>Sale History</b></u>";
        html += "<table>";

        const numericCurrentPrice = currentPrice.replace(/\D/g, '');
        const numericLastSalePrice = transactions[0].soldPrice.replace(/\D/g, '')
        const currentNumericDifference = numericCurrentPrice - numericLastSalePrice;
        const currentPercentageDifference = Math.round(currentNumericDifference / numericLastSalePrice * 100);

        html += `
            <tr>
                <td>Now</td>
                <td>${currentPrice}</td>
                <td>${(currentPercentageDifference > 0 ? '+' : '') + currentPercentageDifference}%</td>
            </tr>
        `;
        
        transactions.forEach(transaction => {
            html += `
                <tr>
                    <td>${transaction.year}</td>
                    <td>${transaction.soldPrice}</td>
                    <td>${transaction.percentageDifference}</td>
                </tr>
            `;
        });

        html += "</table>";
    }

    div.innerHTML = html;

    return div;
}