code: function getNearestDataPoint(mouseX) {
              let points = dataByDate.filter(({date}) => Math.abs(xScale(date) - mouseX) <= epsilon);
  
              if (points.length) {
                  return points[0];
              }
          }
docs: Finds out the data entry that is closer to the given position on pixels
  @param  {Number} mouseX X position of the mouse
  @return {obj}        Data entry that is closer to that x axis position