calc two rectangle's position relation

jquery.ui.intersect.js

$.ui.intersect = function(draggable, droppable, toleranceMode) {

	if (!droppable.offset) return false;

	var x1 = (draggable.positionAbs || draggable.position.absolute).left, x2 = x1 + draggable.helperProportions.width,
		y1 = (draggable.positionAbs || draggable.position.absolute).top, y2 = y1 + draggable.helperProportions.height;
	var l = droppable.offset.left, r = l + droppable.proportions.width,
		t = droppable.offset.top, b = t + droppable.proportions.height;

	switch (toleranceMode) {
		case 'fit':
			return (l <= x1 && x2 <= r
				&& t <= y1 && y2 <= b);
			break;
		case 'intersect':
			return (l < x1 + (draggable.helperProportions.width / 2) // Right Half
				&& x2 - (draggable.helperProportions.width / 2) < r // Left Half
				&& t < y1 + (draggable.helperProportions.height / 2) // Bottom Half
				&& y2 - (draggable.helperProportions.height / 2) < b ); // Top Half
			break;
		case 'pointer':
			var draggableLeft = ((draggable.positionAbs || draggable.position.absolute).left + (draggable.clickOffset || draggable.offset.click).left),
				draggableTop = ((draggable.positionAbs || draggable.position.absolute).top + (draggable.clickOffset || draggable.offset.click).top),
				isOver = $.ui.isOver(draggableTop, draggableLeft, t, l, droppable.proportions.height, droppable.proportions.width);
			return isOver;
			break;
		case 'touch':
			return (
					(y1 >= t && y1 <= b) ||	// Top edge touching
					(y2 >= t && y2 <= b) ||	// Bottom edge touching
					(y1 < t && y2 > b)		// Surrounded vertically
				) && (
					(x1 >= l && x1 <= r) ||	// Left edge touching
					(x2 >= l && x2 <= r) ||	// Right edge touching
					(x1 < l && x2 > r)		// Surrounded horizontally
				);
			break;
		default:
			return false;
			break;
		}

};