simplify addServer/pingHistory & placeholder generation prior to optimizations

lib/servers.js

@@ -113,17 +113,6 @@ class ServerRegistration {
 
   getPingHistory () {
     if (this._pingHistory.length > 0) {
-      const pingHistory = []
-
-      for (let i = 0; i < this._pingHistory.length - 1; i++) {
-        pingHistory[i] = this._pingHistory[i]
-      }
-
-      // Insert the latest update manually into the array
-      // This is a mutated copy of the last update to contain live metadata
-      // The metadata is used by the frontend for rendering
-      const lastPing = this._pingHistory[this._pingHistory.length - 1]
-
       const payload = {
         versions: this.versions,
         recordData: this.recordData,
@@ -138,6 +127,11 @@ class ServerRegistration {
         payload.graphPeakData = graphPeakData
       }
 
+      // Insert the latest update manually into the array
+      // This is a mutated copy of the last update to contain live metadata
+      // The metadata is used by the frontend for rendering
+      const lastPing = this._pingHistory[this._pingHistory.length - 1]
+
       // Conditionally append to avoid defining fields with undefined values
       if (lastPing.result) {
         payload.result = lastPing.result
@@ -145,21 +139,20 @@ class ServerRegistration {
         payload.error = lastPing.error
       }
 
-      // Insert the reconstructed update as the last entry
-      // pingHistory is already sorted during its copy from _pingHistory
-      pingHistory.push(payload)
+      // Send a copy of pingHistory
+      // Omit the last value since it is contained within payload
+      payload.pingHistory = this._pingHistory.slice(0, this._pingHistory.length - 1)
 
-      return pingHistory
+      return payload
     }
 
-    return [{
+    return {
       error: {
-        message: 'Waiting...',
-        placeholder: true
+        message: 'Pinging...'
       },
       recordData: this.recordData,
       graphPeakData: this.getGraphPeak()
-    }]
+    }
   }
 
   loadGraphPoints (points) {