code: function handleMouseMove(e) {
              let [mouseX, mouseY] = getMousePosition(e),
                  dataPoint = isHorizontal ? getNearestDataPoint2(mouseY) : getNearestDataPoint(mouseX),
                  x,
                  y;
  
              if (dataPoint) {
                  // Move verticalMarker to that datapoint
                  if (isHorizontal) {
                      x = mouseX - margin.left;
                      y = yScale(dataPoint.key) + yScale.bandwidth() / 2;
                  } else {
                      x = xScale(dataPoint.key) + xScale2(dataPoint[groupLabel]);
                      y = mouseY - margin.bottom;
                  }
                  moveTooltipOriginXY(x, y);
  
                  // Emit event with xPosition for tooltip or similar feature
                  dispatcher.call('customMouseMove', e, dataPoint, categoryColorMap, x, y);
              }
          }
docs: MouseMove handler, calculates the nearest dataPoint to the cursor
  and updates metadata related to it
  @param  {obj} e the fired event
  @private