JS functions: check if 2 rectangles intersect, are touching, or if one contains the other

collision-detection.js

// Check if rectangle a contains rectangle b
// Each object (a and b) should have 2 properties to represent the
// top-left corner (x1, y1) and 2 for the bottom-right corner (x2, y2).
function contains(a, b) {
	return !(
		b.x1 < a.x1 ||
		b.y1 < a.y1 ||
		b.x2 > a.x2 ||
		b.y2 > a.y2
	);
}

// Check if rectangle a overlaps rectangle b
// Each object (a and b) should have 2 properties to represent the
// top-left corner (x1, y1) and 2 for the bottom-right corner (x2, y2).
function overlaps(a, b) {
	// no horizontal overlap
	if (a.x1 >= b.x2 || b.x1 >= a.x2) return false;

	// no vertical overlap
	if (a.y1 >= b.y2 || b.y1 >= a.y2) return false;

	return true;
}

// Check if rectangle a touches rectangle b
// Each object (a and b) should have 2 properties to represent the
// top-left corner (x1, y1) and 2 for the bottom-right corner (x2, y2).
function touches(a, b) {
	// has horizontal gap
	if (a.x1 > b.x2 || b.x1 > a.x2) return false;

	// has vertical gap
	if (a.y1 > b.y2 || b.y1 > a.y2) return false;

	return true;
}