in js/bootstrap.bundle.js [2935:2954]
function distanceAndSkiddingToXY(placement, rects, offset) {
var basePlacement = getBasePlacement(placement);
var invertDistance = [left, top].indexOf(basePlacement) >= 0 ? -1 : 1;
var _ref = typeof offset === 'function' ? offset(Object.assign({}, rects, {
placement: placement
})) : offset,
skidding = _ref[0],
distance = _ref[1];
skidding = skidding || 0;
distance = (distance || 0) * invertDistance;
return [left, right].indexOf(basePlacement) >= 0 ? {
x: distance,
y: skidding
} : {
x: skidding,
y: distance
};
}