groupBy(): minor refactor

dist/datasource-zabbix/timeseries.js

@@ -83,6 +83,10 @@ System.register(['lodash', './utils'], function (_export, _context) {
   }
 
   function groupBy_perf(datapoints, interval, groupByCallback) {
+    if (datapoints.length === 0) {
+      return [];
+    }
+
     var ms_interval = utils.parseInterval(interval);
     var grouped_series = [];
     var frame_values = [];

dist/test/datasource-zabbix/timeseries.js

@@ -108,6 +108,10 @@ function groupBy(datapoints, interval, groupByCallback) {
 }
 
 function groupBy_perf(datapoints, interval, groupByCallback) {
+  if (datapoints.length === 0) {
+    return [];
+  }
+
   var ms_interval = utils.parseInterval(interval);
   var grouped_series = [];
   var frame_values = [];

src/datasource-zabbix/timeseries.js

@@ -95,6 +95,10 @@ function groupBy(datapoints, interval, groupByCallback) {
 }
 
 function groupBy_perf(datapoints, interval, groupByCallback) {
+  if (datapoints.length === 0) {
+    return [];
+  }
+
   let ms_interval = utils.parseInterval(interval);
   let grouped_series = [];
   let frame_values = [];
@@ -103,8 +107,6 @@ function groupBy_perf(datapoints, interval, groupByCallback) {
   let point_frame_ts = frame_ts;
   let point;
 
-  if (datapoints.length > 0) {
-
   for (let i=0; i < datapoints.length; i++) {
     point = datapoints[i];
     point_frame_ts = getPointTimeFrame(point[POINT_TIMESTAMP], ms_interval);
@@ -127,8 +129,6 @@ function groupBy_perf(datapoints, interval, groupByCallback) {
   frame_value = groupByCallback(frame_values);
   grouped_series.push([frame_value, frame_ts]);
 
-  }
-
   return grouped_series;
 }