j/k for instagram

instagram.js

var index = 0;

function navigate(evt) {
    var media = document.getElementsByTagName('article')[index];
    if (media) {
        index += (evt.key === 'j' ? 1 : (evt.key === 'k' ? -1 : 0));
        media.scrollIntoView();
    }
}

window.addEventListener('keydown', navigate);