add getPeriod function

Author: nicosang

src/dash/DashMetrics.js

@@ -44,10 +44,17 @@ function DashMetrics(config) {
     let dashManifestModel = config.dashManifestModel;
     let manifestModel = config.manifestModel;
 
+    function getPeriod(periodId) {
+        const manifest = manifestModel.getValue();
+        if (!manifest) {
+            return -1;
+        }
+        return manifest.Period_asArray[periodId];
+    }
+
     function getBandwidthForRepresentation(representationId, periodId) {
         let representation;
-        const manifest = manifestModel.getValue();
-        let period = manifest.Period_asArray[periodId];
+        let period = getPeriod(periodId);
 
         representation = findRepresentation(period, representationId);
 
@@ -58,20 +65,16 @@ function DashMetrics(config) {
         return representation.bandwidth;
     }
 
-
     /**
      *
      * @param {string} representationId
      * @param {number} periodIdx
      * @returns {*}
      */
     function getIndexForRepresentation(representationId, periodIdx) {
-        let representationIndex;
-        const manifest = manifestModel.getValue();
-        let period = manifest.Period_asArray[periodIdx];
+        let period = getPeriod(periodIdx);
 
-        representationIndex = findRepresentationIndex(period, representationId);
-        return representationIndex;
+        return findRepresentationIndex(period, representationId);
     }
 
     /**
@@ -84,15 +87,9 @@ function DashMetrics(config) {
      * @instance
      */
     function getMaxIndexForBufferType(bufferType, periodIdx) {
-        let maxIndex;
-        const manifest = manifestModel.getValue();
-        if (!manifest) {
-            return -1;
-        }
-        let period = manifest.Period_asArray[periodIdx];
+        let period = getPeriod(periodIdx);
 
-        maxIndex = findMaxBufferIndex(period, bufferType);
-        return maxIndex;
+        return findMaxBufferIndex(period, bufferType);
     }
 
     /**