code: function handleMouseMove(e) {
              epsilon || setEpsilon();
  
              let [xPosition, yPosition] = d3Selection.mouse(e),
                  dataPoint = getNearestDataPoint(xPosition - margin.left),
                  dataPointXPosition;
  
              if (dataPoint) {
                  dataPointXPosition = xScale(new Date( dataPoint.key ));
                  // Move verticalMarker to that datapoint
                  moveVerticalMarker(dataPointXPosition);
                  // Add data points highlighting
                  highlightDataPoints(dataPoint);
                  // Emit event with xPosition for tooltip or similar feature
                  dispatcher.call('customMouseMove', e, dataPoint, categoryColorMap, dataPointXPosition, yPosition);
              }
          }
docs: MouseMove handler, calculates the nearest dataPoint to the cursor
  and updates metadata related to it
  @private