JavaScript

You can’t get very far in tech without running smack into JavaScript. Chances are, you’re right here, right now because you’ve heard the term and know you need to understand it. The good news is: JavaScript isn’t as scary as it sounds—and yes, you can learn how to use it.

JavaScript: A Quick Definition

JavaScript is a scripting language used to create and control dynamic website content, i.e. anything that moves, refreshes, or otherwise changes on your screen without requiring you to manually reload a web page. Features like:

• animated graphics
• photo slideshows
• autocomplete text suggestions
• interactive forms

An even better way of understanding what JavaScript does is to think about certain web features you use every day and likely take for granted—like when your Facebook timeline automatically updates on your screen or Google suggests search terms based on a few letters you’ve started typing. In both cases, that’s JavaScript in action.

The results of JavaScript may seem simple, but there’s a reason why we teach an entire segment on JavaScript in both our Front End Web Developer and Break into Tech Blueprints. Underneath all those great animations and autocompletes—there’s some pretty fascinating stuff happening. This guide will break down exactly how JavaScript works and why and how to use it, plus the best ways to learn JavaScript if you’re realizing you need it in your skillset.

1. What Is JavaScript? A Detailed Explanation

If you’re hoping to break into a career in tech, your question might sound more like: “What is JavaScript and do I need it?”

If you’re interested in web development—the answer is a resounding yes. So with that out of the way, let’s go a bit deeper into how JavaScript works.

THE POWER OF 3: HTML, CSS, AND JAVASCRIPT

When most people learn to code, they start with good old HTML and CSS. From there, they move on to JavaScript. Which makes sense! The three elements together form the backbone of web development.

For those not familiar:

• HTML is the structure of your page—the headers, the body text, any images you want to include
• CSS controls how that page looks (it’s what you’ll use to customize fonts, background colors, etc.)
• JavaScript is the magic third element. Once you’ve created your structure (HTML) and your aesthetic vibe (CSS), JavaScript makes your site or project dynamic.

JAVASCRIPT IS USED TO AUTOMATE AND ANIMATE

I mentioned above that JavaScript is a “scripting language.” Scripting languages are coding languages used to automate processes that users would otherwise need to execute on their own, step-by-step. Short of scripting, any changes on web pages you visit would require either manually reloading the page, or navigating a series of static menus to get to the content you’re after

A scripting language like JavaScript (JS, for those in the know) does the heavy lifting by telling computer programs like websites or web applications to “do something.” In the case of JavaScript, this means telling those dynamic features described earlier to do whatever it is they do—like telling images to animate themselves, photos to cycle through a slideshow, or autocomplete suggestions to respond to prompts. It’s the “script” in JavaScript that makes these things happen seemingly on their own.

Meanwhile, because JavaScript is such an integral part of web functionality, all major web browsers come with built-in engines that can render JavaScript. This means JS commands can be typed directly into an HTML document, and web browsers will be able to understand them. In other words, using JavaScript doesn’t require downloading any additional programs or compilers.

2. What is JavaScript Used For?

We covered this a bit in the intro, but here’s a quick list of the main things JavaScript is used for.

• Adding interactivity to websites—yup, if you want a website to be more than a static page of text, you’ll need to do some JavaScripting
• Developing mobile applications—JavaScript isn’t just for websites…it’s used to create those apps you have on your phone and tablet as well
• Creating web browser based games—Ever played a game directly from your web browser? JavaScript probably helped make that happen
• Back end web development—yeah, JavaScript is MOSTLY used on the front end of things, but it’s a versatile enough scripting language to be used on back end infrastructure, too.

3. How Does JavaScript Work?

JavaScript is either embedded into a web page or else it’s included in a .js file. JavaScript is also a “client-side” language (rather than a “server-side” language), which is a fancy way of saying that it gets downloaded to site visitors’ computers, then processed.

HOW DO YOU ADD JAVASCRIPT TO A WEBSITE?

Actually adding JavaScript code to a web page is a pretty simple process (and a familiar one if you’ve done any coding with HTML and CSS). JavaScript can be added directly to a page’s code using <script> tags and giving them the type attribute text/javascript. Honestly, JavaScript looks very similar to adding CSS to a site. Here’s a side-by-side comparison:

CSS:

<style> 
CSS goes here
</style>

JavaScript:

<script type="text/javascript">
JavaScript code goes here
</script>

Voila! JavaScript code can also be added to a page as a separate header file with the extension .js (generally done if it’s code that you want to include across a number of pages at once). The script is then downloaded and processed in each individual’s web browser, turning it into the dynamic objects and effects they see on their screen.

One word of warning, though: since JavaScript is processed by individual browsers, it’s possible a user might have JavaScript disabled on their end. Sites that use JavaScript need to have a back up plan in place to avoid breaking when this happens.