JavaScript First Steps
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In our first JavaScript module, we first answer some fundamental questions such as "what is JavaScript?", "what does it look like?", and "what can it do?", before moving on to taking you through your first practical experience of writing JavaScript. After that, we discuss some key building blocks in detail, such as variables, strings, numbers and arrays.

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Prerequisites
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Before starting this module, you don't need any previous JavaScript knowledge, but you should have some familiarity with HTML and CSS. You are advised to work through the following modules before starting on JavaScript:

* Getting started with the Web (which includes a really basic JavaScript introduction).
* Introduction to HTML.
* Introduction to CSS.

**Note:** If you are working on a computer/tablet/other device where you don't have the ability to create your own files, you could try out (most of) the code examples in an online coding program such as JSBin or Glitch.

Guides
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What is JavaScript?

Welcome to the MDN beginner's JavaScript course! In this first article we will look at JavaScript from a high level, answering questions such as "what is it?", and "what is it doing?", and making sure you are comfortable with JavaScript's purpose.

A first splash into JavaScript

Now you've learned something about the theory of JavaScript, and what you can do with it, we are going to give you a crash course on the basic features of JavaScript via a completely practical tutorial. Here you'll build up a simple "Guess the number" game, step by step.

What went wrong? Troubleshooting JavaScript

When you built up the "Guess the number" game in the previous article, you may have found that it didn't work. Never fear — this article aims to save you from tearing your hair out over such problems by providing you with some simple tips on how to find and fix errors in JavaScript programs.

Storing the information you need — Variables

After reading the last couple of articles you should now know what JavaScript is, what it can do for you, how you use it alongside other web technologies, and what its main features look like from a high level. In this article, we will get down to the real basics, looking at how to work with the most basic building blocks of JavaScript — Variables.

Basic math in JavaScript — numbers and operators

At this point in the course, we discuss maths in JavaScript — how we can combine operators and other features to successfully manipulate numbers to do our bidding.

Handling text — strings in JavaScript

Next, we'll turn our attention to strings — this is what pieces of text are called in programming. In this article, we'll look at all the common things that you really ought to know about strings when learning JavaScript, such as creating strings, escaping quotes in strings, and joining them together.

Useful string methods

Now we've looked at the very basics of strings, let's move up a gear and start thinking about what useful operations we can do on strings with built-in methods, such as finding the length of a text string, joining and splitting strings, substituting one character in a string for another, and more.

Arrays

In the final article of this module, we'll look at arrays — a neat way of storing a list of data items under a single variable name. Here we look at why this is useful, then explore how to create an array, retrieve, add, and remove items stored in an array, and more besides.

Assessments
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The following assessment will test your understanding of the JavaScript basics covered in the guides above.

Silly story generator

In this assessment, you'll be tasked with taking some of the knowledge you've picked up in this module's articles and applying it to creating a fun app that generates random silly stories. Have fun!

See also
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Learn JavaScript

An excellent resource for aspiring web developers — Learn JavaScript in an interactive environment, with short lessons and interactive tests, guided by automated assessment. The first 40 lessons are free, and the complete course is available for a small one-time payment.