Edit function: calculate temp diff observations

Remove the logic that throws an error if there is a problem fetching
metadata and observations. It is currently not working as expected

public/js/appChart.js

@@ -7,7 +7,10 @@ import {
 
 import { calculateVorlaufMinusRuecklaufTemperature } from "./src_modules/calculateTemperatureDiff.mjs";
 
-import { getMetadataPlusObservationsFromSingleOrMultipleDatastreams } from "./src_modules/fetchData.mjs";
+import {
+  getMetadataPlusObservationsFromSingleOrMultipleDatastreams,
+  isFetchingRawMetadataPlusObservationsSuccessful,
+} from "./src_modules/fetchData.mjs";
 
 import {
   formatDatastreamMetadataForChart,

public/js/src_modules/calculateTemperatureDiff.mjs

@@ -175,16 +175,6 @@ export const calculateVorlaufMinusRuecklaufTemperature = async function (
           bldgDataPtSamplingRateNestedArr
         );
 
-      // If there is an error in fetching metadata + observations,
-      // the returned array will have this structure: [[undefined, undefined], undefined]
-      // Note that the second element is not an array as we would expect but is a
-      // a single `undefined` value
-      if (typeof observationsPlusMetadata[0][0] === "undefined") {
-        throw new Error(
-          `There was a problem in calculating the temperature difference (dT).\nThis is most likely due to a problem in fetching metadata and observations`
-        );
-      }
-
       // dT observations (timestamp + value)
       const vorlaufMinusRuecklaufTemperatureObs =
         calculateVorlaufMinusRuecklaufTemperatureObservations(

public/js/src_modules/fetchData.mjs

@@ -274,4 +274,31 @@ const getMetadataPlusObservationsFromSingleOrMultipleDatastreams =
     }
   };
 
-export { getMetadataPlusObservationsFromSingleOrMultipleDatastreams };
+/**
+ * Check whether the raw observations and metadata have been successfully fetched, otherwise throw an error
+ *
+ * @param {Array} observationsRawPlusMetadataArr A 1*2 array (the first element is an array that contans N Observations arrays; and the second element is an array of N Datastream metadata objects)
+ * @returns {Boolean} true, if the raw metadata and observations are successfully retrieved, otherwise an error is thrown
+ */
+const isFetchingRawMetadataPlusObservationsSuccessful = function (
+  observationsRawPlusMetadataArr
+) {
+  // If there is an error in fetching metadata + observations (raw observations)
+  // the returned array will have this structure: [[undefined, undefined], undefined]
+  // Note that the second element is not an array as we would expect but is a
+  // a single `undefined` value
+  if (typeof observationsRawPlusMetadataArr[0][0] === "undefined") {
+    throw new Error(
+      `There was a problem in fetching metadata and observations`
+    );
+  }
+  // If metadata + observations fetched successfully
+  else {
+    return true;
+  }
+};
+
+export {
+  getMetadataPlusObservationsFromSingleOrMultipleDatastreams,
+  isFetchingRawMetadataPlusObservationsSuccessful,
+};