function getOffsetRectRelativeToArbitraryNode()

in js/popper-utils.js [395:445]
37 lines of code
11 McCabe index (conditional complexity)

function getOffsetRectRelativeToArbitraryNode(children, parent) {
  var fixedPosition = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : false;

  var isIE10 = isIE(10);
  var isHTML = parent.nodeName === 'HTML';
  var childrenRect = getBoundingClientRect(children);
  var parentRect = getBoundingClientRect(parent);
  var scrollParent = getScrollParent(children);

  var styles = getStyleComputedProperty(parent);
  var borderTopWidth = parseFloat(styles.borderTopWidth, 10);
  var borderLeftWidth = parseFloat(styles.borderLeftWidth, 10);

  // In cases where the parent is fixed, we must ignore negative scroll in offset calc
  if (fixedPosition && isHTML) {
    parentRect.top = Math.max(parentRect.top, 0);
    parentRect.left = Math.max(parentRect.left, 0);
  }
  var offsets = getClientRect({
    top: childrenRect.top - parentRect.top - borderTopWidth,
    left: childrenRect.left - parentRect.left - borderLeftWidth,
    width: childrenRect.width,
    height: childrenRect.height
  });
  offsets.marginTop = 0;
  offsets.marginLeft = 0;

  // Subtract margins of documentElement in case it's being used as parent
  // we do this only on HTML because it's the only element that behaves
  // differently when margins are applied to it. The margins are included in
  // the box of the documentElement, in the other cases not.
  if (!isIE10 && isHTML) {
    var marginTop = parseFloat(styles.marginTop, 10);
    var marginLeft = parseFloat(styles.marginLeft, 10);

    offsets.top -= borderTopWidth - marginTop;
    offsets.bottom -= borderTopWidth - marginTop;
    offsets.left -= borderLeftWidth - marginLeft;
    offsets.right -= borderLeftWidth - marginLeft;

    // Attach marginTop and marginLeft because in some circumstances we may need them
    offsets.marginTop = marginTop;
    offsets.marginLeft = marginLeft;
  }

  if (isIE10 && !fixedPosition ? parent.contains(scrollParent) : parent === scrollParent && scrollParent.nodeName !== 'BODY') {
    offsets = includeScroll(offsets, parent);
  }

  return offsets;
}