Chapter 10: Optimize Async samples

2020-08-31 01:24:43 +01:00
parent 52d632f0d2
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+const MongoClient = require("mongodb").MongoClient;
+const URL = "mongodb://localhost:27017/";
+
+MongoClient.connect(URL, { useUnifiedTopology: true }, (err, client) => {
+  if (err) throw err;
+
+  const db = client.db("data");
+  const values = db.collection("values");
+  const averages = db.collection("averages");
+
+  values.find({}).toArray((err, data) => {
+    if (err) throw err;
+
+    // Calculate average
+    const average =
+      data.reduce((accumulator, value) => accumulator + value.value, 0) /
+      data.length;
+
+    averages.find({}).toArray((err) => {
+      if (err) throw err;
+
+      averages.insertOne({ value: average }, (err) => {
+        if (err) throw err;
+        console.log("Stored average in database.");
+        client.close();
+      });
+    });
+  });
+});