File download function for modern browsers ( = excluding IE)

downloadExecute.js

function downloadExecute(downloadURL) {
    fetch(downloadURL)
    .then(function(response) {
        return response.blob();
    }).then(function(blob) {
        var fileBlob = new Blob([blob], {type: blob.type});
        var aLink = document.createElement("a");
        aLink.href = window.URL.createObjectURL(fileBlob);
        aLink.download = decodeEntity(pageData.fileName);
        aLink.click();
    });
}