download-google-timeline.js

(async function() {
    async function fetchData(date) {
        var date_split = date.split('-'),
            year = date_split[0],
            month = date_split[1],
            day = date_split[2];
        if (parseInt(day) < 10){
            day = parseInt(day);
        }
        month = parseInt(month) - 1;
        var url = "https://www.google.com/maps/timeline/kml?authuser=0&pb=!1m8!1m3!1i"+year+"!2i"+month+"!3i"+day+"!2m3!1i"+year+"!2i"+month+"!3i"+day;
        const data = await fetch(url);
        const xml = await data.text();
        return xml;
    }

    function download(filename, text) {
    var element = document.createElement('a');
    element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
    element.setAttribute('download', filename);

    element.style.display = 'none';
    document.body.appendChild(element);

    element.click();

    document.body.removeChild(element);
    }

    const dates = [
        await fetchData('2020-08-03'),
        await fetchData('2020-08-02')
    ];
    download('google-location-history.json', JSON.stringify({ dates }, null, 2));
}());