LEARNYOUNODE

Learn the basics of node: asynchronous i/o, http.

An introduction to Node.js via a set of self-guided workshops

These are my solutions to the exercises about dealing with synchronous & asynchronous I/O, filesystem operations, TCP and HTTP networking, events and streams. I have implemented my solutions using TypeScript. To transpile the TypeScript files to JavaScript files, use the following command (at the root of your direcory):

    tsc your-typescript-file.ts --target es2019 --outfile output-javascript-file.js

To verify the solutions, run the following command and the tests associated with your exercise will be executed:

    learnyounode verify your-solution-file.js

NodeSchool

Workshopper is the name used for the open source lesson modules associated with NodeSchool. You can find these exercises/workshoppers by visiting the NodeSchool page

The Workshopper associated with this repo is called learnyounode.

Getting Started

To get started with this workshopper, run the following command to install the learnyounode package globally.

    npm install -g learnyounode

Start up learnyounode in your terminal by running the command learnyounode in your preferred directory

    learnyounode

To install type definitions for Node.js, run this:

    npm install --save @types/node

Alternatively, if you are running the programs in this repo, just run the following command and you'll have the type definitions (plus any other dependency) installed:

    npm install

Notes

Process

The process object provides information about, and control over the current Node.js process. The process object is an instance of EventEmitter. What does this mean?

Well, much of the Node.js core API is built around an asynchronous event-driven architecture in which certain kinds of objects, "emmiters", emit named events that cause Function objects, "Listeners", to be called. For instance, fs.ReadStream emits an event when the file is opened.

All objects that emit events are instances of the EventEmitter class, this applies to our process object. To learn more about events associaed with this process object, please visit the documentation page.

process.argv is a property that returns an string array containing the command-line arguments passed when the associated Node.js process was launched.

The first argument will be process.execPath which is a property that returns the absolute pathname of the executable that started the Node.js process.
The second argument will be the path to the javascript file being executed.
The remaining elements will be any additional command-line arguments.

File System

The node:fs module enables interacting with the file system. To perform a file system operation you are going to need this fs module from the node core library.

All file system operations have synchronous(blocking), callback and promise-based forms.

Promise-based operations - These return a promise that is fulfilled when the async operation is complete.
The callback form - These take a completion callback function as their last argument and invoke the operation asynchronously. The arguments passed to the completion callback depend on the method, but the first argument is always reserved for an exception. If the operation is completed successfully, then the first argument is null or undefined.
Synchronous APIs - The synchronous APIs perform all operations synchronously, blocking the event loop until the operation completes or fails. The synchronous(blocking) filesystem methods in the fs module end with Sync.

NOTE: The callback-based versions of the node:fs module APIs perform better(both in terms of execution time and memory allocation) compared to the promise-based operations.

Samueelx / learnyounode