NodeJs Intro Review

## Client-Side JavaScript - **Client-Side JavaScript**: Code that runs on the client side of a web application, usually in a web browser. - **Limitations of Client-Side JavaScript**: While powerful, client-side JavaScript has certain limitations: - Very restricted access to local files. - Not designed for handling complex application logic. - Potential security concerns (e.g., exposing sensitive information like database credentials). - **Reason for Limitations**: These limitations exist because client-side JavaScript was initially designed to run exclusively on web browsers. ## Browser Environment - **JavaScript Engine**: Web browsers provide the environment needed to run JavaScript code, including the JavaScript Engine. - **Document Object Model (DOM)**: Browsers provide access to the DOM, allowing you to access HTML elements in your code. - **Historical Context**: Previously, JavaScript could not run outside of a browser, but now it can with Node.js. ## What is Node.js? - **Node.js**: A JavaScript runtime environment. Officially defined as "an open-source and cross-platform JavaScript runtime environment." - **Open Source**: Node.js code is publicly available and maintained by a large community of developers. - **Cross-Platform**: Works on any operating system, including Windows, macOS, and Linux. - **JavaScript Runtime Environment**: Allows you to run JavaScript code outside of a browser. ## Node.js Use Cases - **Common Applications**: Node.js is used across a wide range of industries for: - Building web servers and APIs that handle HTTP requests. - Developing web and mobile applications. - Handling complex data and database interactions. - **Industry Adoption**: If you are using or developing a website or web application that interacts with a database or handles complex data, there is a high chance that you will use Node.js behind the scenes. - **Key Characteristics**: Node.js is efficient, scalable, and has a large community of developers and maintainers around the world. ## Browser vs. Node Runtime Environment - **Browser Environment**: Primarily designed for front-end web development, runs client-side JavaScript. - **Node Runtime Environment**: Primarily designed for back-end web development, runs server-side JavaScript. - **API Differences**: The environment determines the APIs available: - **Browser**: Access to the DOM API, but restrictions for accessing the local file system. - **Node**: Access to almost all system resources, including the file system, but not the DOM. ## Global Objects - **Browser Global Object (`window`)**: Provides access to browser-related functionalities: - Methods for manipulating the DOM. - Managing cookies. - Handling browser events. - **Node.js Global Object (`global`)**: Provides access to Node.js specific functionalities: - Built-in modules for working with local files. - Networking capabilities. - Interacting with the operating system. ## Version Control - **Browser Version**: You have no control over the version of the browser environment that your users will use to visit your website. - **Node.js Version**: You can choose the version of Node.js that you want to use in your server. ## Importance of Node.js - **Full-Stack Development**: Node.js has transformed web development by enabling developers to use JavaScript to build both the front-end and the back-end of full-stack applications. - **Efficiency**: The development process is more efficient because developers don't need to learn a new programming language just for developing the back-end. - **Impact**: Node.js is a powerful, scalable, and versatile tool that has become very important for developers worldwide. ## Advantages of Node.js - **Single Language for Full-Stack**: You can implement both the front-end and the back-end of a web application using JavaScript. - Reduces the initial learning curve. - No need to switch between programming languages. - Increases efficiency and productivity. - **Non-Blocking, Event-Driven Architecture**: Great for developing real-time applications where responsiveness and efficiency are essential for creating a good user experience. - **Single Thread and Event Loop**: Can effectively handle a large number of simultaneous requests and Input-Output operations. - Perfect for applications that require handling multiple requests simultaneously. - **Large Community**: Thousands of developers around the world constantly maintain Node.js and add new features. - Many learning resources available. - Easy to find answers to questions. - **npm (Node Package Manager)**: A powerful tool that allows you to install and manage packages and modules for your projects. - Packages available for many purposes: handling HTTP requests, working with databases, formatting dates and times, testing code, and more. - Reuse code written, tested, and shared by other developers. - Makes workflow faster and more efficient. - **Cost-Effective**: Node.js is free and open source. - Packages, libraries, and associated tools are also primarily free. - Important factor when optimizing budget. ## Disadvantages of Node.js - **Single-Threaded Limitation**: Only runs one thread at a time, meaning it can only handle one operation at a time. - While architecture allows efficient handling of concurrent (simultaneous) requests, CPU-intensive tasks may block the main thread and result in performance issues. - Examples of CPU-intensive tasks: complex mathematical operations, image and video processing, cryptography. - Ways to overcome this exist, but usually increase application complexity. - **Asynchronous Programming**: Node.js relies on asynchronous programming. - A task that may take a long time to run is started, but instead of waiting until it's completed, the main program continues running while the asynchronous task runs in parallel. - When the task is completed, the program handles the result. - Often involves "callbacks," which are functions that define what happens when asynchronous operations are completed. - Can potentially make code more difficult to read, understand, and debug. - **Package Quality Concerns**: When choosing packages from npm, some may not be constantly maintained and may introduce vulnerabilities into your application. - Developers should evaluate each package carefully. - Check if packages follow quality and security best practices. ## Threads - **Thread**: A path of execution within a process, like a computer program that is currently running. ## NVM (Node Version Manager) - **NVM**: A tool for managing multiple versions of Node.js on the same computer. - **Purpose**: Helps you switch between different versions of Node.js for different projects easily. - **Recommendation**: Installing NVM before Node.js is recommended for future flexibility. ## Installing NVM on macOS/Linux - **Xcode Command Line Tools (macOS)**: Must be manually installed before running the NVM install script on macOS. ```bash xcode-select --install ``` - **Verify Xcode Installation**: ```bash xcode-select --version ``` - **Download and Execute NVM Installation Script**: Run one of these commands: ```bash curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash ``` ```bash wget -qO- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash ``` - **Terminal Restart**: You might need to restart your terminal when the process is completed to load the new command and configuration. - **Verify NVM Installation**: ```bash nvm -v ``` ## Installing Node.js with NVM on macOS/Linux - **Install Latest LTS Version**: To install the latest Long-Term Support (LTS) version of Node.js: ```bash nvm install --lts ``` - **LTS (Long-Term Support)**: This version is usually recommended because it prioritizes stability, reliability, and security over new or experimental features. - Thoroughly tested and ready for production. - Guaranteed to have longer support periods with a focus on bug fixes and security patches. - **Install Specific Version**: You can install a specific version of Node.js by specifying the version number: ```bash nvm install <version> ``` Example: ```bash nvm install 20 ``` - **Switch to a Version**: ```bash nvm use <version> ``` Example: ```bash nvm use 20 ``` - **Check Current Node.js Version**: ```bash node -v ``` ## Installing NVM on Windows - **Official NVM Support**: Official versions of NVM only support Windows in specific cases. - If you have Windows Subsystem for Linux (WSL), you can follow the macOS/Linux guide above. - **nvm-windows**: A Node.js version management utility for Windows. - Completely separate project from the official NVM project. - Same purpose: help you work with multiple versions of Node.js on the same device. - **Before Installing**: It is recommended to uninstall any prior Node installation before installing NVM for Windows. - **Installation Steps**: - Go to the Releases section of the official repository: `https://github.com/coreybutler/nvm-windows/releases`. - Download the latest installer. - Follow the instructions. - **Terminal Restart**: You might need to restart your terminal if the `nvm` command is not immediately available. - **Verify Installation**: ```powershell nvm -v ``` ## Installing Node.js using NVM for Windows - **Install Latest LTS Version**: ```powershell nvm install lts ``` - **Install Specific Version**: ```powershell nvm install <version> ``` Example: ```powershell nvm install 20 ``` - **Switch to a Version**: ```powershell nvm use <version> ``` Example: ```powershell nvm use 20 ``` - **Check Current Node.js Version**: ```bash node -v ``` ## Basic NVM and Node.js Commands - **Note on Commands**: All commands work for NVM installed on macOS/Linux, including WSL. They may work differently or may not work at all for `nvm-windows`. Alternative commands for `nvm-windows` are provided when possible. ### PowerShell Execution Policy (Windows) - **Default Execution Policy**: PowerShell's default execution policy is `Restricted`, which prevents scripts from running as a security measure. - **Run PowerShell as Administrator**: Right-click on PowerShell, then click "Run as Administrator". - **Check Current Execution Policy**: ```powershell Get-ExecutionPolicy ``` - **Set Execution Policy to RemoteSigned**: Allows local scripts and `npm` to run: ```powershell Set-ExecutionPolicy RemoteSigned ``` - **After Setting Policy**: Close the administrator window of PowerShell and open a non-admin PowerShell window. ### List All Installed Versions - **List Installed Versions**: To list all installed versions of Node.js and check the one that is currently being used: ```bash nvm ls ``` ### Set Default Node.js Version (NVM on macOS/Linux Only) - **Set Default Version**: Sets the default version of Node.js for new terminal sessions: ```bash nvm alias default <version> ``` Example: ```bash nvm alias default 22.20.0 ``` - **Create Custom Aliases**: Assign a more specific name to a version: ```bash nvm alias <new_name> <version> ``` Example: ```bash nvm alias new-api 18.20.8 ``` - **Use Custom Alias**: ```bash nvm use <new_name> ``` Example: ```bash nvm use new-api ``` ### Remove a Version of Node.js - **Uninstall a Version**: ```bash nvm uninstall <version> ``` Example: ```bash nvm uninstall 20.19.5 ``` - **Remove by Major Version (NVM on macOS/Linux)**: You can remove a version by running the `uninstall` command with a major version like `22` or `20`: ```bash nvm uninstall 20 ``` If you have multiple releases for that major version installed, like `20.14.0` and `20.12.2`, the latest version will be removed first. Running `nvm uninstall 20` will remove `20.14.0` first. ### Check Node.js Version - **Check Current Version**: ```bash node -v ``` ### Check npm Version - **npm**: A package manager for Node.js used to install, publish, and manage software packages. Automatically installed when you install Node.js. - **Check npm Version**: ```bash npm -v ``` ### Run a JavaScript File - **Execute JavaScript File**: Runs the JavaScript file in the currently active Node.js runtime: ```bash node <file.js> ``` Example: ```bash node app.js ``` ### Create a Node.js Project - **Initialize Project**: Creates a new Node.js project by creating a `package.json` file that tracks its details and dependencies: ```bash npm init ``` - **Interactive Setup**: The `npm init` command walks you through an interactive CLI guide for setting up the `package.json` file. - Asks questions for project name, description, version, etc. - **Default Setup**: To start with a default `package.json` file: ```bash npm init -y ``` or ```bash npm init --yes ``` ### Install a Package - **Install Specific Package**: ```bash npm install <package> ``` Example: ```bash npm install express ``` ### Install All Dependencies - **Install Dependencies**: To install all dependencies listed in the `package.json` file of a project: ```bash npm install ```