[mmotor]

function download(filename, text) {
    var blob = new Blob([text], {type:'text/csv'}),
        link = document.createElement('a');
        link.href = URL.createObjectURL(blob);
        link.setAttribute('download', filename);
        var event = document.createEvent('MouseEvents');
        event.initEvent('click', true, true);
        link.dispatchEvent(event);
}
download('test.txt', 'Hello world! Hello world!');

В IE не работает