problem_185.js

/**
 * Determines area overlap of two rectangles
 * @param  {Object} rec1
 * @param  {Object} rec2
 * @return {number}
 */
function calcRectangleOverlap(rec1, rec2) {
  // find top left corner for rec 1
  const [x1, y1] = rec1.top_left;
  const [height1, width1] = rec1.dimensions;
  const x2 = x1 + height1;
  const y2 = y1 + width1;

  // find top left corner for rec 1
  const [x3, y3] = rec2.top_left;
  const [height2, width2] = rec2.dimensions;
  const x4 = x3 + height1;
  const y4 = y3 + width1;

  if (!isOverlap([x1, y1, x2, y2], [x3, y3, x4, y4])) return 0;

  // Area of 1st Rectangle
  const area1 = Math.abs(x1 - x2) * Math.abs(y1 - y2);

  // Area of 2nd Rectangle
  const area2 = Math.abs(x3 - x4) * Math.abs(y3 - y4);

  const areaI =
    Math.min(x2, x4) - Math.max(x1, x3) * (Math.min(y2, y4) - Math.max(y1, y3));

  return area1 + area2 - areaI;
}

/**
 * Determines if rectangles overlap
 * @param  {number[]}  rec1
 * @param  {number[]}  rect2
 * @return {boolean}
 */
function isOverlap(rec1, rec2) {
  return (
    Math.min(rec1[2], rec2[2]) > Math.max(rec1[0], rec2[0]) && // width > 0
    Math.min(rec1[3], rec2[3]) > Math.max(rec1[1], rec2[1]) // height > 0
  );
}

const obj1 = {
  top_left: [1, 4],
  dimensions: [3, 3]
};

const obj2 = {
  top_left: [0, 5],
  dimensions: [4, 3]
};

console.log(calcRectangleOverlap(obj1, obj2));