Check thumbs js fetch

check_thumbs.js

function handleErrors(response) {
    if (!response.ok) {
        throw Error(response.statusText);
    }
    return response;
}

let thumbs = [];
fetch("http://master.demo.geonode.org/api/layers/")
    .then(r => r.json()).then(data => {
        thumbs = data.objects.map(x => [ x['title'],x['thumbnail_url'] ])
    })
    .then(data => {
        for (let i in thumbs) {
            fetch(thumbs[i][1]).then(handleErrors).then(function(response) {
                console.log(`${i} OK: ${thumbs[i][0]}`);
        }).catch(function(error) {
            console.warn(`${error} ${thumbs[i][0]}`);
           });
    }
})
.catch(e => console.log(e))