JavaScript Tutorial for Beginners: Learn Javascript in 5 Days

Javascript Training Summary

JavaScript is an open source & most popular client side scripting language supported by all browsers. JavaScript is used mainly for enhancing the interaction of a user with the webpage. This online guide is geared to make you a JavaScript pro!

What should I know?

Nothing! This is an absolute beginners guide to JavaScript.

How do JavaScript engines work?

JavaScript Engines are complicated. But it works on some simple basics:

The engine reads ("parses:) the script.
Then it converts or compiles the script to the machine language.
After that machine code runs.

Here, JavaScript engine applies optimizations at each step of the process. It reads a compiled script and analyzes the data that passes in JavaScript engine. After that, it applies optimizations to the machine code from that acquired knowledge. When this process is completed, scripts run quite fast.

What can in-browser JavaScript do?

JavaScript's functionality depends on the environment it's running in. For example, Node.js supports functions which allows JavaScript to read and write arbitrary files, perform network requests, object-oriented, etc. The roles that JavaScript plays in both client-side (front end) and server-side (back end) development of applications can vary wildly.

In-browser JavaScript also allows you to perform webpage manipulation, interaction with the user and with the web server.

Javascript offer advantages like:

Show dynamic content based on the user profile.
React to user's operations, like mouse clicks events, key presses or pointer movements.
Support features like auto-validated form entries and interactive drop-down menus.
Send requests to remote servers, Upload and download files.
JavaScript code can also create movement and sound
Ask questions to the users, Get and set cookies, show messages, switch browser tabs.
Allows the data on to be stored in the local storage.

What can't in-browser JavaScript do?

JavaScript's capabilities in the browser are quite limited for the sake of the user's safety. It helps to prevent any unauthorized webpage from accessing private information.

Examples of such limitations are:

JavaScript on a webpage may not allow you to copy, execute or read/write arbitrary files on the hard disk. It doesn't offer any access to Operating system functions.
Many browsers allow it to work with files, but the access is very limited and only provided if the user is performing a specific action like, dropping a file into a browser window or selecting using <input> tag.
JavaScript allows you to communicate over the net to the server where the current page came from. Although, it does not allow you to receive data from other sites/domains.

What makes JavaScript unique?

Here, are the three most important features which make JavaScript unique

It offers full integration with HTML/CSS.
Simple things are done quickly without any complication or following strict rules.
Supported by all major browsers and JavaScript is enabled by default.

Alternatives to JavaScript

The syntax of JavaScript not suited for everyone as different project demands different features. However, some modern tool like a Coffee script, Typescript, and Dart allowing developers to code in another language and then auto-convert into the JavaScript code.

Where is JavaScript Today?

ECMAScript is a specification governed by ECMA international aimed at standardizing JavaScript. The latest version is ECMA9 also called JavaScript 9. It is supported by all major browsers like Chrome, Firefox, Internet Explorer, etc. Though each browser has an array of unique commands that are not part of the standards.