New function: get index of missing observations

Currently, this function is only available in the scope of the
function that formats observations for the scatter plot chart.

Get the index of the observations that are available in the first
array but are missing from the second array.

public/js/appChart.js

@@ -846,6 +846,29 @@ const formatSTAResponseForScatterPlot = function (obsArrayOne, obsArrayTwo) {
     obsArrayTwoTimestamp
   );
   console.log(missingTimestamp);
+
+  /**
+   *
+   * @param {Array} missingTimestampsArr An array of strings representing the missing timestamps
+   * @param {Array} firstObsTimestampArr An array of timestamps for the first set of observations
+   * @returns {Array} An array of the indexes of the missing observations
+   */
+  const getIndexOfMissingObservation = function (
+    missingTimestampsArr,
+    firstObsTimestampArr
+  ) {
+    const indexesMissingObs = missingTimestampsArr.map((index) =>
+      firstObsTimestampArr.indexOf(index)
+    );
+
+    // console.log(indexes);
+    return indexesMissingObs;
+  };
+
+  const indexesMissingObsArr = getIndexOfMissingObservation(
+    missingTimestamp,
+    obsArrayOneTimestamp
+  );
 };
 
 (async () => {