Skip to content

'An Introduction to JavaScript'' minor tweaks following plain language guidelines #3337

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
p2635 wants to merge 6 commits into
base: master
Choose a base branch
from
Open

'An Introduction to JavaScript'' minor tweaks following plain language guidelines #3337

Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
142c54d
Replaced 'such'
p2635 Jan 28, 2023
33e477c
Change 'we' to 'you' to be more direct
p2635 Jan 28, 2023
88e595e
Simplify 'able to' to 'can'
p2635 Jan 28, 2023
e7b1f0c
Change' 'plethora' to 'many' for plain language
p2635 Jan 28, 2023
ee3ccab
Removed unnecessary extra words
p2635 Jan 28, 2023
a3d7595
Restructure flow
p2635 Jan 28, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
34 changes: 17 additions & 17 deletions 1-js/01-getting-started/1-intro/article.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,24 +1,24 @@
# An Introduction to JavaScript

Let's see what's so special about JavaScript, what we can achieve with it, and what other technologies play well with it.
Let's see what's so special about JavaScript, what you can achieve with it, and what other technologies play well with it.

## What is JavaScript?

*JavaScript* was initially created to "make web pages alive".

The programs in this language are called *scripts*. They can be written right in a web page's HTML and run automatically as the page loads.

Scripts are provided and executed as plain text. They don't need special preparation or compilation to run.
JavaScript is very different from another language called [Java](https://en.wikipedia.org/wiki/Java_(programming_language)).

In this aspect, JavaScript is very different from another language called [Java](https://en.wikipedia.org/wiki/Java_(programming_language)).
Scripts are provided and executed as plain text. They don't need special preparation or compilation to run.

```smart header="Why is it called <u>Java</u>Script?"
When JavaScript was created, it initially had another name: "LiveScript". But Java was very popular at that time, so it was decided that positioning a new language as a "younger brother" of Java would help.

But as it evolved, JavaScript became a fully independent language with its own specification called [ECMAScript](http://en.wikipedia.org/wiki/ECMAScript), and now it has no relation to Java at all.
As it evolved, JavaScript became a fully independent language with its own specification called [ECMAScript](http://en.wikipedia.org/wiki/ECMAScript), and now it has no relation to Java at all.
```

Today, JavaScript can execute not only in the browser, but also on the server, or actually on any device that has a special program called [the JavaScript engine](https://en.wikipedia.org/wiki/JavaScript_engine).
Today, JavaScript can execute not only in the browser, but also on the server, or on any device that has a special program called [the JavaScript engine](https://en.wikipedia.org/wiki/JavaScript_engine).

The browser has an embedded engine sometimes called a "JavaScript virtual machine".

Expand All @@ -35,8 +35,8 @@ The terms above are good to remember because they are used in developer articles
Engines are complicated. But the basics are easy.

1. The engine (embedded if it's a browser) reads ("parses") the script.
2. Then it converts ("compiles") the script to machine code.
3. And then the machine code runs, pretty fast.
2. It converts ("compiles") the script to machine code.
3. The machine code runs, pretty fast.

The engine applies optimizations at each step of the process. It even watches the compiled script as it runs, analyzes the data that flows through it, and further optimizes the machine code based on that knowledge.
```
Expand All @@ -49,7 +49,7 @@ JavaScript's capabilities greatly depend on the environment it's running in. For

In-browser JavaScript can do everything related to webpage manipulation, interaction with the user, and the webserver.

For instance, in-browser JavaScript is able to:
For instance, in-browser JavaScript can:

- Add new HTML to the page, change the existing content, modify styles.
- React to user actions, run on mouse clicks, pointer movements, key presses.
Expand All @@ -61,7 +61,7 @@ For instance, in-browser JavaScript is able to:

JavaScript's abilities in the browser are limited to protect the user's safety. The aim is to prevent an evil webpage from accessing private information or harming the user's data.

Examples of such restrictions include:
Examples of restrictions include:

- JavaScript on a webpage may not read/write arbitrary files on the hard disk, copy them or execute programs. It has no direct access to OS functions.

Expand All @@ -70,14 +70,14 @@ Examples of such restrictions include:
There are ways to interact with the camera/microphone and other devices, but they require a user's explicit permission. So a JavaScript-enabled page may not sneakily enable a web-camera, observe the surroundings and send the information to the [NSA](https://en.wikipedia.org/wiki/National_Security_Agency).
- Different tabs/windows generally do not know about each other. Sometimes they do, for example when one window uses JavaScript to open the other one. But even in this case, JavaScript from one page may not access the other page if they come from different sites (from a different domain, protocol or port).

This is called the "Same Origin Policy". To work around that, *both pages* must agree for data exchange and must contain special JavaScript code that handles it. We'll cover that in the tutorial.
This is called the "Same Origin Policy". To work around that, *both pages* must agree for data exchange and contain special JavaScript code that handles it. You'll learn that in the tutorial.

This limitation is, again, for the user's safety. A page from `http://anysite.com` which a user has opened must not be able to access another browser tab with the URL `http://gmail.com`, for example, and steal information from there.
- JavaScript can easily communicate over the net to the server where the current page came from. But its ability to receive data from other sites/domains is crippled. Though possible, it requires explicit agreement (expressed in HTTP headers) from the remote side. Once again, that's a safety limitation.

![](limitations.svg)

Such limitations do not exist if JavaScript is used outside of the browser, for example on a server. Modern browsers also allow plugins/extensions which may ask for extended permissions.
These limitations do not exist if JavaScript is used outside of the browser, for example on a server. Modern browsers also allow plugins/extensions which may ask for extended permissions.

## What makes JavaScript unique?

Expand All @@ -96,15 +96,15 @@ That said, JavaScript can be used to create servers, mobile applications, etc.

## Languages "over" JavaScript

The syntax of JavaScript does not suit everyone's needs. Different people want different features.
The JavaScript syntax does not suit everyone's needs. Different people want different features.

That's to be expected, because projects and requirements are different for everyone.
That's expected, because projects and requirements are different for everyone.

So, recently a plethora of new languages appeared, which are *transpiled* (converted) to JavaScript before they run in the browser.
Recently many new languages appeared, which are *transpiled* (converted) to JavaScript before they run in the browser.

Modern tools make the transpilation very fast and transparent, actually allowing developers to code in another language and auto-converting it "under the hood".
Modern tools make the transpilation very fast and transparent, allowing developers to code in another language and auto-converting it "under the hood".

Examples of such languages:
Examples of these languages:

- [CoffeeScript](https://coffeescript.org/) is "syntactic sugar" for JavaScript. It introduces shorter syntax, allowing us to write clearer and more precise code. Usually, Ruby devs like it.
- [TypeScript](https://www.typescriptlang.org/) is concentrated on adding "strict data typing" to simplify the development and support of complex systems. It is developed by Microsoft.
Expand All @@ -113,7 +113,7 @@ Examples of such languages:
- [Brython](https://brython.info/) is a Python transpiler to JavaScript that enables the writing of applications in pure Python without JavaScript.
- [Kotlin](https://kotlinlang.org/docs/reference/js-overview.html) is a modern, concise and safe programming language that can target the browser or Node.

There are more. Of course, even if we use one of these transpiled languages, we should also know JavaScript to really understand what we're doing.
There are more. Of course, even if you use one of these transpiled languages, you should also know JavaScript to really understand what you're doing.

## Summary

Expand Down