function getDataset(e) {
    return new Map(Object.entries(e.dataset));
}

function getDatasetValuesArray(e) {
    return Object.entries(e.dataset).map(([, value]) => value);
}


for ( let e of document.querySelectorAll('p') ) {
    let datasetValuesArray = getDatasetValuesArray(e);
    e.textContent = datasetValuesArray.join(", ");
}

<p data-one="foo">...</p>
<p data-one="bar" data-two="baz">...</p>