# JavaScript

> The programming language that runs inside web pages and makes them interactive.

- Level: Basic
- Topics: Software
- URL: https://tidbit.legios.com.ar/javascript/
- In Spanish: [JavaScript](https://tidbit.legios.com.ar/es/javascript/)

**JavaScript** is the programming language built into every web browser. HTML says what is on a page and CSS says how it looks; JavaScript says what it does. When a menu opens, a form warns you that the email is missing, or a map lets you drag it around without reloading, JavaScript is doing that work on your own device.

It was created in 1995 at Netscape, in a famously short time, and its official standard is called **ECMAScript**. Despite the name, it has nothing to do with Java; the name was a marketing choice of the era. Because every browser has to run the same JavaScript, the standard changes carefully, and old code keeps working.

Today JavaScript also runs outside the browser, on servers and in desktop and phone apps, through runtimes like Node.js. That means one language can power both the frontend and the backend of a product, which is a big reason it is among the most used languages in the world. Many teams write **TypeScript**, a stricter version that adds type checks and is translated into plain JavaScript before it runs.

## An analogy

If a web page were a theater play, HTML would be the script, CSS the costumes and set, and JavaScript the actors reacting to the audience.

## Keep in mind

- Every web browser runs JavaScript; no installation needed.
- Not related to Java despite the name.
- Its standard is ECMAScript; TypeScript is a typed variant that compiles to it.
- Also runs on servers through runtimes like Node.js.

## Go deeper

- [What is JavaScript? (MDN)](https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/Scripting/What_is_JavaScript)
- [JavaScript reference and guides (MDN)](https://developer.mozilla.org/en-US/docs/Web/JavaScript)
- [JavaScript on Wikipedia](https://en.wikipedia.org/wiki/JavaScript)

## Related terms

- [Programming language](https://tidbit.legios.com.ar/programming-language/): A precise, written language people use to give instructions to a computer.
- [Web browser](https://tidbit.legios.com.ar/web-browser/): The app that fetches web pages from the internet and draws them on your screen.
- [HTML](https://tidbit.legios.com.ar/html/): The text format that describes what is on a web page: headings, paragraphs, links.
- [CSS](https://tidbit.legios.com.ar/css/): The language that decides how a web page looks: colors, fonts, spacing, layout.
- [Server](https://tidbit.legios.com.ar/server/): A computer whose job is to answer requests from other computers, all day, every day.
- [Frontend and backend](https://tidbit.legios.com.ar/frontend-and-backend/): The part of an app you see and touch, and the part that works behind it.