isbefore.jquery.js

$.fn.isBefore = function(e2) {
	// var all = $(context || document).find("*");
	// return all.index(this[0]) < all.index($(sel));
	let e1 = $(this).get(0);
	e2 = $(e2).get(0);
	let p1 = $(e1).parents(); // returns a jQuery object
	let p2 = $(e2).parents(); // ordrered from the immediate parent up
	for (var i1 = 0; i1 < p1.length; i1++) {
		let i2 = p2.index(p1[i1]);
		if (i2 >= 0) {
			let commonParent = p1[i1];
			// take e as common sibling if common parent is index 0
			let common1 = i1 > 0 ? p1[i1 - 1] : e1;
			let common2 = i2 > 0 ? p2[i2 - 1] : e2;
			if (common2 === e1) {
				return true; // parent before child
			}
			let $commonSiblings = $(commonParent).find('>*');
			return $commonSiblings.index(common1) < $commonSiblings.index(common2);
		}
	}
	return false;
};

// Example
// $('#something').isBefore('#somethingElse')