streamline some functions

assets/src/scripts/monitoring-location/components/hydrograph/selectors/domain.js

@@ -177,6 +177,13 @@ export const getFullArrayOfAdditionalTickMarks = function(tickValues, yDomain) {
     return Array.from(new Set(additionalTickValues.concat(tickValues)));
 };
 
+
+/**
+ * Redux selector function to find the maximum and minimum of all data values displayed on the primary y-axis. Information
+ * which can then be used to determine the correct values for numbering the tick marks of the primary y-axis.
+ * @return {Array}  An array with two values representing the lowest and highest values for the primary
+ * y-axis. Defaults to a range of 0 to 1 if there are no values.
+ */
 export const getPrimaryValueRange = createSelector(
     isVisible('compare'),
     isVisible('median'),
@@ -187,7 +194,6 @@ export const getPrimaryValueRange = createSelector(
     getPrimaryParameter,
     (showCompare, showMedian, primaryRange, compareRange, medianRange, gwLevelsRange, parameter) => {
         const valueExtent = [];
-        let result = [0, 1];
         if (primaryRange) {
             valueExtent.push(...primaryRange);
         }
@@ -200,30 +206,26 @@ export const getPrimaryValueRange = createSelector(
         if (showMedian && medianRange) {
             valueExtent.push(...medianRange);
         }
-        if (valueExtent.length) {
-            result = [Math.min(...valueExtent), Math.max(...valueExtent)];
 
-            // Add padding to the extent and handle empty data sets.
-            result = extendDomain(result, useSymlog(parameter));
-        }
-        return result;
+        return valueExtent.length ?
+            extendDomain([Math.min(...valueExtent), Math.max(...valueExtent)], useSymlog(parameter)) : [0, 1];
     }
 );
 
 
-
+/**
+ * Redux selector function to find the maximum and minimum of all data values displayed on the secondary y-axis. Information
+ * which can then be used to determine the correct values for numbering the tick marks of the secondary y-axis.
+ * @return {Array} secondaryYAxisDomain - array with two values, representing the lowest and highest values for the secondary
+ * y-axis. Defaults to a range of 0 to 1 if there are no values.
+ */
 export const getSecondaryValueRange = createSelector(
     getIVDataRange('secondary'),
     getIVParameter('secondary'),
     (secondaryParameterRange, secondaryParameter) => {
-        let result = [0, 1];
-        if (secondaryParameterRange) {
-            result = [Math.min(...secondaryParameterRange), Math.max(...secondaryParameterRange)];
-
-            // Add padding to the extent and handle empty data sets.
-            result = extendDomain(secondaryParameterRange, useSymlog(secondaryParameter));
-        }
-        return result;
+        return secondaryParameterRange ?
+            extendDomain([Math.min(...secondaryParameterRange), Math.max(...secondaryParameterRange)], useSymlog(secondaryParameter)) :
+            [0, 1];
     }
 );
 
@@ -240,10 +242,10 @@ const getYTickDetails = memoize(tickKind => createSelector(
     getPrimaryParameter,
     getSecondaryValueRange,
     getIVParameter('secondary'),
-    (primaryDomain, primaryParameter, secondaryYDomain, SecondaryParameter) => {
+    (primaryDomain, primaryParameter, secondaryYDomain, secondaryParameter) => {
 
-        const parameter = tickKind === 'primary' ? primaryParameter : SecondaryParameter;
-        const yDomain = tickKind === 'primary' ? primaryDomain : secondaryYDomain;
+        const parameter = tickKind === 'secondary' ? secondaryParameter : primaryParameter;
+        const yDomain = tickKind === 'secondary' ? secondaryYDomain : primaryDomain;
 
         let tickValues = ticks(yDomain[0], yDomain[1], Y_TICK_COUNT);