Chapter 3: Samples

Chapter03/learning-streams/async-generator.js

@@ -0,0 +1,15 @@
+const { Readable } = require("stream");
+
+async function* generate() {
+  yield "Node.js";
+  yield "is";
+  yield "a";
+  yield "JavaScript";
+  yield "Runtime";
+}
+
+const readable = Readable.from(generate());
+
+readable.on("data", (chunk) => {
+  console.log(chunk);
+});

Chapter03/learning-streams/for-await-read-stream.js

@@ -0,0 +1,12 @@
+const fs = require("fs");
+
+const rs = fs.createReadStream("./file.txt");
+
+async function run() {
+  for await (const chunk of rs) {
+    console.log("Read chunk:", chunk);
+  }
+  console.log("No more data.");
+}
+
+run();

Chapter03/learning-streams/infinite-read.js

@@ -0,0 +1,9 @@
+const fs = require("fs");
+
+const rs = fs.createReadStream("/dev/urandom");
+
+let size = 0;
+rs.on("data", (data) => {
+  size += data.length;
+  console.log("File size:", size);
+});

Chapter03/learning-streams/paused-stream.js

@@ -0,0 +1,16 @@
+const fs = require("fs");
+
+const rs = fs.createReadStream("./file.txt");
+
+rs.on("readable", () => {
+  // Read data
+  let data = rs.read();
+  while (data !== null) {
+    console.log("Read chunk:", data);
+    data = rs.read();
+  }
+});
+
+rs.on("end", () => {
+  console.log("No more data.");
+});

Chapter03/learning-streams/read-stream.js

@@ -0,0 +1,11 @@
+const fs = require("fs");
+
+const rs = fs.createReadStream("./file.txt");
+
+rs.on("data", (data) => {
+  console.log("Read chunk:", data.toString());
+});
+
+rs.on("end", () => {
+  console.log("No more data.");
+});

Chapter03/learning-streams/write-stream.js

@@ -0,0 +1,9 @@
+const fs = require("fs");
+
+const file = fs.createWriteStream("./file.txt");
+
+for (let i = 0; i <= 1000000; i++) {
+  file.write(
+    "Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.\n"
+  );
+}

Chapter03/object-streams/object-stream.js

@@ -0,0 +1,14 @@
+const { Transform } = require("stream");
+const { stringify } = require("ndjson");
+
+const Name = Transform({
+  objectMode: true,
+  transform: ({ forename, surname }, encoding, callback) => {
+    callback(null, { name: forename + " " + surname });
+  },
+});
+
+Name.pipe(stringify()).pipe(process.stdout);
+
+Name.write({ forename: "John", surname: "Doe" });
+Name.write({ forename: "Jane", surname: "Doe" });

Chapter03/object-streams/package-lock.json

@@ -0,0 +1,79 @@
+{
+  "name": "object-streams",
+  "version": "1.0.0",
+  "lockfileVersion": 1,
+  "requires": true,
+  "dependencies": {
+    "inherits": {
+      "version": "2.0.4",
+      "resolved": "https://registry.npmjs.org/inherits/-/inherits-2.0.4.tgz",
+      "integrity": "sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ=="
+    },
+    "json-stringify-safe": {
+      "version": "5.0.1",
+      "resolved": "https://registry.npmjs.org/json-stringify-safe/-/json-stringify-safe-5.0.1.tgz",
+      "integrity": "sha1-Epai1Y/UXxmg9s4B1lcB4sc1tus="
+    },
+    "minimist": {
+      "version": "1.2.5",
+      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
+      "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw=="
+    },
+    "ndjson": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/ndjson/-/ndjson-2.0.0.tgz",
+      "integrity": "sha512-nGl7LRGrzugTtaFcJMhLbpzJM6XdivmbkdlaGcrk/LXg2KL/YBC6z1g70xh0/al+oFuVFP8N8kiWRucmeEH/qQ==",
+      "requires": {
+        "json-stringify-safe": "^5.0.1",
+        "minimist": "^1.2.5",
+        "readable-stream": "^3.6.0",
+        "split2": "^3.0.0",
+        "through2": "^4.0.0"
+      }
+    },
+    "readable-stream": {
+      "version": "3.6.0",
+      "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.6.0.tgz",
+      "integrity": "sha512-BViHy7LKeTz4oNnkcLJ+lVSL6vpiFeX6/d3oSH8zCW7UxP2onchk+vTGB143xuFjHS3deTgkKoXXymXqymiIdA==",
+      "requires": {
+        "inherits": "^2.0.3",
+        "string_decoder": "^1.1.1",
+        "util-deprecate": "^1.0.1"
+      }
+    },
+    "safe-buffer": {
+      "version": "5.2.1",
+      "resolved": "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.2.1.tgz",
+      "integrity": "sha512-rp3So07KcdmmKbGvgaNxQSJr7bGVSVk5S9Eq1F+ppbRo70+YeaDxkw5Dd8NPN+GD6bjnYm2VuPuCXmpuYvmCXQ=="
+    },
+    "split2": {
+      "version": "3.2.2",
+      "resolved": "https://registry.npmjs.org/split2/-/split2-3.2.2.tgz",
+      "integrity": "sha512-9NThjpgZnifTkJpzTZ7Eue85S49QwpNhZTq6GRJwObb6jnLFNGB7Qm73V5HewTROPyxD0C29xqmaI68bQtV+hg==",
+      "requires": {
+        "readable-stream": "^3.0.0"
+      }
+    },
+    "string_decoder": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz",
+      "integrity": "sha512-hkRX8U1WjJFd8LsDJ2yQ/wWWxaopEsABU1XfkM8A+j0+85JAGppt16cr1Whg6KIbb4okU6Mql6BOj+uup/wKeA==",
+      "requires": {
+        "safe-buffer": "~5.2.0"
+      }
+    },
+    "through2": {
+      "version": "4.0.2",
+      "resolved": "https://registry.npmjs.org/through2/-/through2-4.0.2.tgz",
+      "integrity": "sha512-iOqSav00cVxEEICeD7TjLB1sueEL+81Wpzp2bY17uZjZN0pWZPuo4suZ/61VujxmqSGFfgOcNuTZ85QJwNZQpw==",
+      "requires": {
+        "readable-stream": "3"
+      }
+    },
+    "util-deprecate": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz",
+      "integrity": "sha1-RQ1Nyfpw3nMnYvvS1KKJgUGaDM8="
+    }
+  }
+}

Chapter03/object-streams/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "object-streams",
+  "version": "1.0.0",
+  "description": "",
+  "main": "object-stream.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "ndjson": "^2.0.0"
+  }
+}

Chapter03/piping-streams/file.txt

@@ -0,0 +1,4 @@
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.
+

Chapter03/piping-streams/pipe-stream.js

@@ -0,0 +1,5 @@
+const fs = require("fs");
+
+const rs = fs.createReadStream("file.txt");
+
+rs.pipe(process.stdout);

Chapter03/stream-pipelines/file.txt

@@ -0,0 +1,3 @@
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.

Chapter03/stream-pipelines/newFile.txt

@@ -0,0 +1,3 @@
+NODE.JS IS A JAVASCRIPT RUNTIME BUILT ON GOOGLE CHROME'S V8 JAVASCRIPT ENGINE.
+NODE.JS IS A JAVASCRIPT RUNTIME BUILT ON GOOGLE CHROME'S V8 JAVASCRIPT ENGINE.
+NODE.JS IS A JAVASCRIPT RUNTIME BUILT ON GOOGLE CHROME'S V8 JAVASCRIPT ENGINE.

Chapter03/stream-pipelines/pipeline.js

@@ -0,0 +1,22 @@
+const fs = require("fs");
+const { pipeline, Transform } = require("stream");
+
+const uppercase = new Transform({
+  transform(chunk, encoding, callback) {
+    // Data processing
+    callback(null, chunk.toString().toUpperCase());
+  },
+});
+
+pipeline(
+  fs.createReadStream("./file.txt"),
+  uppercase,
+  fs.createWriteStream("./newFile.txt"),
+  (err) => {
+    if (err) {
+      console.error("Pipeline failed.", err);
+    } else {
+      console.log("Pipeline succeeded.");
+    }
+  }
+);

Chapter03/stream-pipelines/promise-pipeline.js

@@ -0,0 +1,25 @@
+const fs = require("fs");
+const stream = require("stream");
+const util = require("util");
+
+const pipeline = util.promisify(stream.pipeline);
+
+const uppercase = new stream.Transform({
+  transform(chunk, encoding, callback) {
+    // Data processing
+    callback(null, chunk.toString().toUpperCase());
+  },
+});
+
+async function run() {
+  await pipeline(
+    fs.createReadStream("./file.txt"),
+    uppercase,
+    fs.createWriteStream("./newFile.txt")
+  );
+  console.log("Pipeline succeeded.");
+}
+
+run().catch((err) => {
+  console.error("Pipeline failed.", err);
+});

Chapter03/transform-stream/file.txt

@@ -0,0 +1,3 @@
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.
+Node.js is a JavaScript runtime built on Google Chrome's V8 JavaScript engine.

Chapter03/transform-stream/newFile.txt

@@ -0,0 +1,3 @@
+NODE.JS IS A JAVASCRIPT RUNTIME BUILT ON GOOGLE CHROME'S V8 JAVASCRIPT ENGINE.
+NODE.JS IS A JAVASCRIPT RUNTIME BUILT ON GOOGLE CHROME'S V8 JAVASCRIPT ENGINE.
+NODE.JS IS A JAVASCRIPT RUNTIME BUILT ON GOOGLE CHROME'S V8 JAVASCRIPT ENGINE.

Chapter03/transform-stream/transform-stream-es6.js

@@ -0,0 +1,18 @@
+const fs = require("fs");
+const { Transform } = require("stream");
+
+const rs = fs.createReadStream("./file.txt");
+const newFile = fs.createWriteStream("./newFile.txt");
+
+class Uppercase extends Transform {
+  constructor() {
+    super();
+  }
+
+  _transform(chunk, encoding, callback) {
+    this.push(chunk.toString().toUpperCase());
+    callback();
+  }
+}
+
+rs.pipe(new Uppercase()).pipe(newFile);

Chapter03/transform-stream/transform-stream.js

@@ -0,0 +1,15 @@
+const fs = require("fs");
+const { Transform } = require("stream");
+
+const rs = fs.createReadStream("./file.txt");
+
+const newFile = fs.createWriteStream("./newFile.txt");
+
+const uppercase = new Transform({
+  transform(chunk, encoding, callback) {
+    // Data processing
+    callback(null, chunk.toString().toUpperCase());
+  },
+});
+
+rs.pipe(uppercase).pipe(newFile);