Keyboard navigation for Instagram timeline

instagram.js

/*
A userscript to add keyboard shortcuts to the Instagram timeline:
- J or space to go to next image
- K to go to previous image
- L to toggle like on the current image
- N to load new posts
*/
$(document.body).keypress(function(event) {

	// ignore keypresses in comment fields
	if(document.activeElement.tagName == 'INPUT') {
		return;
	}

	// get the image currently at the top of the window
	var current = null;
	var items = $('article');
	items.each(function(index, element) {
		if(!current && element.offsetTop + element.offsetHeight > document.body.scrollTop) {
			current = $(element);
		}
	});
	
	if(!current) {
		// something weird happened, or you're not on the timeline
		return;
	}
	
	var key = String.fromCharCode(event.which).toUpperCase();
	
	if(key == 'N') {
		// N for new posts
		if($('.timelineTopPaginate').length) {
			$('.timelineTopPaginate')[0].click();
		} else {
			document.body.scrollTop = 0;
		}
		return;
	}
	
	if(key == 'L') {
		// L for like
		$('.timelineLikeButton', current.parents('.timelineItem'))[0].click();
		return;
	}
	
	// get the next or previous item
	var target = null;
	if(key == 'J' || key == ' ') {
		// J or space for next
		target = items[items.index(current) + 1];
	} else if(key == 'K') {
		// K for back
		target = items[items.index(current) - 1];
	}

	if(!target) {
		// you're at the beginning or end
		return;
	}

	// scroll to the new item
	event.preventDefault();
	document.body.scrollTop = target.offsetTop + $('nav')[0].offsetHeight;
	
	if(items.index(target) == items.length - 2) {
		// load more
		$('a.-cx-PRIVATE-AutoloadingPostsGrid__moreLink')[0].click();
	}
});