var activityData = {
 "dataSourceId": "derived:com.google.distance.delta:com.google.android.gms:pruned_distance",
 "point": [
 ...
 ]
};
 
var distanceData = {
 "dataSourceId": "derived:com.google.activity.segment:com.google.android.gms:merge_activity_segments",
 "point": [
 ...
 ]
};

  var gFitUtils = require('googlefit-rest-utils');
  var distanceByBucket = gFitUtils.bucketByActivityType(distanceData.point, activityData.point);