Understanding JavaScript
Tags: javascript, webdev, beginners, tutorial
Published: 2024-04-21 07:27:20

Let's try to understand the basics of JavaScript.

JavaScript is a synchronous single-threaded programming language.

**What is a single-threaded language?**
A single-threaded language means that it can only execute one piece of code at a time. In other words, it has a single call stack where it pushes and pops functions during execution. This is different from languages like Java or C++, which can have multiple threads running concurrently.

**What is synchronous execution?**
Synchronous execution means that code is executed line by line, and each line of code must wait for the previous line to complete before moving to the next one. This can lead to blocking issues when dealing with long-running operations like network requests or file system operations.

Let's consider an example:

![example](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/k3gu8vnsw28mgqkqbdl3.png)
Output:

![output of the above example](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/rn8r0lrl3fj181dckqo1.png)

Explanation: 
In the given code, the first thing that happens is that console.log("first") is executed, and the word "first" is printed to the console.

Next, the for loop starts executing.First, console.log("first statement") is executed, printing "first statement" to the console.
Then, console.log("second statement") is executed, printing "second statement" to the console.

After the code inside the loop runs once, the loop ends, and JavaScript moves on to the next line of code, which is console.log("second"). This prints the word "second" to the console.

because JavaScript is a single-threaded language, It cannot start a new task until the previous task is completed. This is called synchronous execution, where each line of code must wait for the previous line to finish before it can run.

If there are many lines of code or a long-running task inside the loop, JavaScript will have to execute all of them before moving on to the next part of the code. During this time, JavaScript will be blocked and unable to perform any other tasks, such as responding to user interactions or handling events.

In the past, JavaScript was mainly used inside web browsers to add interactive features to websites. However, these days, JavaScript can do much more than that. Thanks to a special program called a JavaScript engine, JavaScript code can now run on various devices and platforms, not just web browsers.

Now, let's break it down further:

A JavaScript engine is a program that understands and executes JavaScript code. Web browsers have built-in JavaScript engines that allow them to run JavaScript and make websites interactive. For example, when you click a button on a website, it's the JavaScript engine in your browser that makes the button respond to your click.

However, JavaScript engines are not limited to web browsers. There are other programs and platforms that also have JavaScript engines built-in or included. This means that developers can write JavaScript code, and these platforms can execute that code, just like a web browser.

One popular example is Node.js, which allows developers to run JavaScript code on servers and build server-side applications like APIs, web servers, and more. The Node.js platform includes a JavaScript engine called V8, which is the same engine used by the Google Chrome web browser.