Basic JavaScript You Should Know

What is JavaScript?

JavaScript is a high-level language. Its also known as a single-threaded, non-blocking and asynchronous concurrent language. It is a versatile language that runs on the client side (in web browsers) as well as on the server side (with the help of platforms like Node.js).

JavaScript enables developers to add dynamic and interactive elements to web pages, allowing for enhanced user experiences. It provides capabilities for manipulating and modifying HTML and CSS, handling user events, making network requests, and performing calculations.

What is JavaScript Engine?

A JavaScript engine is a computer program or virtual machine that executes JavaScript code. It is responsible for interpreting and running JavaScript instructions, converting them into machine-readable instructions that can be executed by the computer's hardware.

JavaScript engines are typically found in web browsers, where they handle the execution of JavaScript code embedded within web pages. These engines parse and analyze the JavaScript code, optimize it, and then execute it efficiently.

Some popular JavaScript engines used in web browsers include:

1. V8: Developed by Google, V8 is the JavaScript engine used in Google Chrome and is known for its high-performance execution.

2. SpiderMonkey: SpiderMonkey is the JavaScript engine used in Mozilla Firefox. It was the first JavaScript engine ever created and remains a widely used option.

3. JavaScriptCore: JavaScriptCore, also known as Nitro, is the JavaScript engine used in Apple's Safari web browser.

4. Chakra: Chakra is the JavaScript engine used in older versions of Microsoft Edge.

These engines continuously evolve to improve performance, memory management, and support for new JavaScript features. They play a critical role in executing JavaScript code efficiently and enabling the rich interactive experiences we see on the web today.

How does JavaScript work?

JavaScript is a client-side scripting language that runs in web browsers. When a web page is loaded, the browser's JavaScript engine takes over and executes the JavaScript code present on the page. Here's a simplified overview of how JavaScript works:

1. Parsing: JavaScript code is parsed by the JavaScript engine to understand its structure and syntax.

2. Execution Context: An execution context is created to keep track of variables, functions, and other necessary information.

3. Variable and Function Hoisting: Declarations of variables and functions are moved to the top of their respective scopes during the creation of the execution context.

4. Execution: The JavaScript engine executes the code line by line, performing calculations, manipulating data, and interacting with the DOM.

5. Event-driven Programming: JavaScript responds to user interactions by listening for events and executing specific code when events occur.

6. Asynchronous Operations: JavaScript supports asynchronous tasks like network requests, using callbacks, Promises, or async/await syntax.

7. Garbage Collection: JavaScript engines have garbage collectors that reclaim memory from unused objects to manage memory efficiently.

It's worth noting that JavaScript can also run outside web browsers, using platforms like Node.js for server-side scripting and building applications beyond the browser environment.