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Objectives of this JavaScript tutorial and prerequisites

Welcome to this new course about the JavaScript programming language.

This tutorial is accessible to all and may be beneficial to everyone, whether you are already an expert in JavaScript or a complete neophyte.

The only prerequisite for taking this course is to already have good knowledge of HTML and CSS, otherwise you will not be able to follow this tutorial.

If you do not know HTML or CSS at all, I invite you to go first and follow my complete tutorial on these two languages here.: HTML, CSS

The objectives of this course are primarily to introduce you to how JavaScript works and to introduce you to the possibilities offered by this language.

Methodology and pedagogy

In order to simplify your learning, this course has been divided into parts themselves divided into chapters each studying a specific aspect of JavaScript.

You can access any chapter via the summary on your left.

This course follows a logical schema and begins by presenting simple mechanisms of JavaScript to gradually move towards the more complex. I recommend that you follow all chapters in order.

To optimize your learning, this course uses several media including video. Indeed, you will have at the beginning of each chapter a related video.

I also try to illustrate my lessons as much as possible because, let things be said immediately: you can learn to actually code only by practicing and being faced with difficulties.

What is JavaScript?

JavaScript is a programming language created in 1995.

JavaScript will allow us to create interactive and "live" pages using scripts.

A script is simply a sequence of instructions that will be interpreted by a program.

So, to read JavaScript code, we will need an interpreter. Fortunately, all browsers (Google Chrome, Safari, etc.) have their own JavaScript interpreter.

JavaScript, a client-side language

JavaScript is a programming language called "client-side".

There are two main types of programming languages: client-side languages and server-side languages.

The client-side languages will run on the client side, that is, on the computer of the person who will request the web page.

The server-side languages, on the other hand, will run on the server side. A server is a kind of very powerful computer that will store web pages and send them to the client when he requests them.

For example, when you search on Google, you are the customer and you request via your browser to access a web page. This web page is stored on a server that will send it to you.

The client-side and server-side languages do not have the same purpose. In fact, the client rarely interacts directly with server-side languages (like PHP for example) because they are often there to perform calculations and process data in the background.

The important thing at the moment is that you retain the following schema:

1. You ask to access a web page via your browser. You are the client and the web page is stored on the server;
2. The server receives your request. The server-side languages will run on the server side (calculations, etc.);
3. Once the execution is complete, the server returns the web page which contains only client-side code (the server-side languages perform their operations and return client-side code), including possibly JavaScript;
4. The execution of client-side languages is done when you receive the requested page in your browser.

Remember, however, that projects have come into use to use server-side JavaScript (CommonJs, Node.js). We will not talk about it in this class.