# Introduction to Javascript

## What is Javascript?

Javascript is a programming language that enables you to create dynamically updating content, control multimedia etc.

### JavaScript engine

It is a software component that executes js code.

earlier js engines were interpreters but all relevant modern engines use JUST-IN-TIME compilation for improved performance.

Developed by web browser vendors, every major browser has one JS engine.

Js engine work in concert with the rendering engine via the DOM

**What is a Rendering Engine?**

Rendering engine or browser engine or layout engine: core software component of every major web browser.

The browser engine's primary job is to transform HTML documents and other resources of a web page into an interactive visual representation on a user's device.

the browser has an embedded engine that they use sometimes known as a “Javascript virtual machine”.

example:

chrome, opera, Edge use the V8 engine firefox

use- spider monkey.

#### **How does an engine work?**

engines read the script

it converts that script into machine code

then machine code run, pretty fast

### **what makes js unique?**

1. full integration with HTML and css
    
2. simple things are done simply
    
3. supported by all major browsers and enabled by default.