sw-9.js

function urlBase64ToUint8Array(base64String) {
    const padding = '='.repeat((4 - base64String.length % 4) % 4);
    const base64 = (base64String + padding)
        .replace(/\-/g, '+')
        .replace(/_/g, '/');

    const rawData = window.atob(base64);
    const outputArray = new Uint8Array(rawData.length);

    for (let i = 0; i < rawData.length; ++i)  {
        outputArray[i] = rawData.charCodeAt(i);
    }
    return  outputArray;
}

fetch('./app_pubkey')
    .then(function(res) {
        res.json().then(function(data) {  
            var appPubkey = data.key;
            registerPush(urlBase64ToUint8Array(appPubkey));
        });
    });