chapter 2: initial samples

Chapter02/working-with-files/callback-hell.js

@@ -0,0 +1,5 @@
+first(args, function () {
+    second(args, function () {
+        third(args, function () {})
+    })
+})

Chapter02/working-with-files/hello.txt

@@ -0,0 +1 @@
+HELLO WORLD!

Chapter02/working-with-files/readWriteAsync.js

@@ -0,0 +1,16 @@
+const fs = require('fs');
+const path = require('path')
+
+const filepath = path.join(process.cwd(), 'hello.txt');
+
+fs.readFile(filepath, 'utf8', function (err, contents) {
+    if (err) {
+        return console.log(err);
+    }
+    console.log("File Contents:", contents);
+    contents = contents.toUpperCase();
+    fs.writeFile(filepath, contents, function (err) {
+        if (err) throw err;
+        console.log("File updated.")
+    });
+});

Chapter02/working-with-files/readWriteAsync2.js

@@ -0,0 +1,20 @@
+const fs = require('fs');
+const path = require('path')
+
+const filepath = path.join(process.cwd(), 'hello.txt');
+
+fs.readFile(filepath, 'utf8', function (err, contents) {
+    if (err) {
+        return console.log(err);
+    }
+    console.log("File Contents:", contents);
+    contents = contents.toUpperCase();
+    updateFile(filepath, contents);
+});
+
+function updateFile(filepath, contents) {
+    fs.writeFile(filepath, contents, function (err) {
+        if (err) throw err;
+        console.log("File updated.");
+    });
+};

Chapter02/working-with-files/readWritePromise.js

@@ -0,0 +1,15 @@
+const fs = require("fs").promises;
+const path = require('path');
+
+const filepath = path.join(process.cwd(), 'hello.txt');
+
+async function run() {
+    try {
+        const contents = await fs.readFile(filepath, 'utf8');
+        console.log("File Contents:", contents);
+    } catch (error) {
+        console.error(error);
+    }
+};
+
+run();

Chapter02/working-with-files/readWriteSync.js

@@ -0,0 +1,12 @@
+const fs = require('fs');
+const path = require('path');
+
+const filepath = path.join(process.cwd(), 'hello.txt');
+
+let contents = fs.readFileSync(filepath, 'utf8');
+console.log("File Contents:", contents);
+
+contents = contents.toString().toUpperCase();
+
+fs.writeFileSync(filepath, contents);
+console.log("File updated.");