What is an HTTP request in JavaScript? (Built-in requests)

An HTTP (HyperText Transfer Protocol) request is a network message that a client (such as a browser or JavaScript runtime) sends to a server to retrieve or send data. HTTP requests are the foundation of the web, enabling communication between clients and servers.

JavaScript, as the primary language for web development, has built-in mechanisms for making HTTP requests, allowing code to seamlessly communicate over the network by performing asynchronous or synchronous requests.

Key features of built-in HTTP requests:

• Asynchronous Execution: Allows making network requests without blocking the UI, ensuring smooth and fast performance
• Request Configuration: Provides full control over HTTP methods (GET, POST, PUT, DELETE, PATCH), headers, and body formats (JSON, FormData, Blob, etc.)
• Response Handling: Offers versatile methods for processing responses, such as JSON.parse, Blob, text, arrayBuffer
• Error Handling: Includes systematic management of network errors, HTTP errors, and timeouts

These mechanisms are available in web browsers and the Node.js environment (with different APIs in Node.js). In this context, we'll primarily focus on native methods used in browsers: XMLHttpRequest and Fetch API.

A brief historical overview:

• The XMLHttpRequest (XHR) API was created in the 2000s for Ajax (Asynchronous JavaScript and XML) technology. It allowed developers to make network requests without page reloads, revolutionizing web interactivity.
• The Fetch API was introduced later as a more modern, Promise-based method, providing a simpler and cleaner API that works better in async/await contexts and offers more convenient ways to manage requests and responses.

Thus, HTTP requests in JavaScript are included as powerful, dynamic network interfaces essential for the smooth and modern operation of any web application.

Next, we'll examine XMLHttpRequest in more detail to understand how it works at a lower level, its limitations, and how to use it.