improve glucose-get-last performance

lib/glucose-get-last.js

@@ -1,36 +1,41 @@
+
 function getDateFromEntry(entry) {
   return entry.date || Date.parse(entry.display_time) || Date.parse(entry.dateString);
 }
 
 var getLastGlucose = function (data) {
-    data = data.filter(function(obj) {
-      return obj.glucose || obj.sgv;
-    }).map(function prepGlucose (obj) {
-        //Support the NS sgv field to avoid having to convert in a custom way
-        obj.glucose = obj.glucose || obj.sgv;
-        if ( obj.glucose !== null ) {
-            return obj;
-        }
-    });
-
-    var now = data[0];
-    var now_date = getDateFromEntry(now);
+    var now = undefined;
+    var now_date = undefined;
     var change;
     var last_deltas = [];
     var short_deltas = [];
     var long_deltas = [];
     var last_cal = 0;
 
     //console.error(now.glucose);
-    for (var i=1; i < data.length; i++) {
+    for (var i=0; i < data.length; i++) {
         // if we come across a cal record, don't process any older SGVs
-        if (typeof data[i] !== 'undefined' && data[i].type === "cal") {
+        var item = data[i];
+        item.glucose = item.glucose || item.sgv;
+        if (!item.glucose) {
+            continue;
+        }
+        if (typeof now === 'undefined') {
+            now = item;
+            now_date = getDateFromEntry(item);
+            continue;
+        }
+        if (typeof now === 'undefined') {
+            continue;
+        }
+        if (item.type === "cal") {
             last_cal = i;
             break;
         }
+
         // only use data from the same device as the most recent BG data point
-        if (typeof data[i] !== 'undefined' && data[i].glucose > 38 && data[i].device === now.device) {
-            var then = data[i];
+        if (item.glucose > 38 && item.device === now.device) {
+            var then = item;
             var then_date = getDateFromEntry(then);
             var avgdelta = 0;
             var minutesago;
@@ -39,7 +44,10 @@ var getLastGlucose = function (data) {
                 // multiply by 5 to get the same units as delta, i.e. mg/dL/5m
                 change = now.glucose - then.glucose;
                 avgdelta = change/minutesago * 5;
-            } else { console.error("Error: date field not found: cannot calculate avgdelta"); }
+            } else {
+                console.error("Error: date field not found: cannot calculate avgdelta");
+                continue;
+            }
             //if (i < 5) {
                 //console.error(then.glucose, minutesago, avgdelta);
             //}
@@ -60,6 +68,8 @@ var getLastGlucose = function (data) {
             // long_deltas are calculated from everything ~20-40 minutes ago
             } else if (17.5 < minutesago && minutesago < 42.5) {
                 long_deltas.push(avgdelta);
+            } else if (minutesago > 42.5) {
+                break;
             }
         }
     }