chore: working on chapter 4

04-asynchronous-control-flow-patterns-with-callbacks/01-web-spider/spider-cli.js

@@ -3,7 +3,10 @@ import { spider } from './spider.js'
 spider(process.argv[2], (err, filename, downloaded) => {
   if (err) {
     console.error(err)
-  } else if (downloaded) {
+    process.exit(1)
+  }
+
+  if (downloaded) {
     console.log(`Completed the download of "${filename}"`)
   } else {
     console.log(`"${filename}" was already downloaded`)

04-asynchronous-control-flow-patterns-with-callbacks/02-web-spider-callback-discipline/README.md

@@ -7,5 +7,5 @@ Refactored version of web spider that cleans up callback hell.
 Install the necessary dependencies with `npm install` and then run:
 
 ```bash
-node spider-cli.js https://loige.co
+node spider-cli.js https://loige.co 3
 ```

04-asynchronous-control-flow-patterns-with-callbacks/02-web-spider-callback-discipline/spider-cli.js

@@ -3,7 +3,10 @@ import { spider } from './spider.js'
 spider(process.argv[2], (err, filename, downloaded) => {
   if (err) {
     console.error(err)
-  } else if (downloaded) {
+    process.exit(1)
+  }
+
+  if (downloaded) {
     console.log(`Completed the download of "${filename}"`)
   } else {
     console.log(`"${filename}" was already downloaded`)

04-asynchronous-control-flow-patterns-with-callbacks/02-web-spider-callback-discipline/spider.js

@@ -21,7 +21,7 @@ function download(url, filename, cb) {
       if (err) {
         return cb(err)
       }
-      cb(null)
+      cb(null, content)
     })
   })
 }

04-asynchronous-control-flow-patterns-with-callbacks/03-sequential-execution/README.md

@@ -0,0 +1,11 @@
+# 03-sequential-execution
+
+Simple example that demonstrates sequential tasks using callbacks
+
+## Run
+
+Run:
+
+```bash
+node index.js
+```

04-asynchronous-control-flow-patterns-with-callbacks/03-sequential-execution/index.js

@@ -0,0 +1,26 @@
+function asyncOperation(cb) {
+  process.nextTick(cb)
+}
+
+function task1(cb) {
+  asyncOperation(() => {
+    task2(cb)
+  })
+}
+
+function task2(cb) {
+  asyncOperation(() => {
+    task3(cb)
+  })
+}
+
+function task3(cb) {
+  asyncOperation(() => {
+    cb() // finally executes the callback
+  })
+}
+
+task1(() => {
+  // executed when task1, task2 and task3 are completed
+  console.log('tasks 1, 2 and 3 executed')
+})

04-asynchronous-control-flow-patterns-with-callbacks/03-sequential-execution/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "03-sequential-execution",
+  "version": "1.0.0",
+  "description": "Simple example that demonstrates sequential tasks using callbacks",
+  "engines": {
+    "node": ">=22"
+  },
+  "engineStrict": true,
+  "type": "module",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}

04-asynchronous-control-flow-patterns-with-callbacks/04-web-spider-v2/README.md

@@ -0,0 +1,11 @@
+# 04-web-spider-v2
+
+Web spider example to demonstrate sequential iteration
+
+## Run
+
+Install the necessary dependencies with `npm install` and then run:
+
+```bash
+node spider-cli.js https://loige.co
+```