Introduction to Web Development

Introduction to Web Development

How do you make content for the web? Through this workshop series you will be creating your own, personal website. This will cover:


While computer science students are encouraged to attend, no coding experience is necessary. If you've ever wanted to learn some coding, this is a great way to start!

Set up instructions

To do these workshops, you'll need a text editor and a modern web browser.

For a text editor, we recommend Visual Studio Code. You can install it from the website.

The latest version of Google Chrome, Safari, Edge or Firefox will work for a web browser, you are probably already using one of these.

In a hurry? You can create a website right in the browser. Try JSBin.

Contributors: Christian Silver, Martin Hartt, Eliot Lim, Mara Mihali, Lucia Bura, Patrick Ferris
View slides
View video recording
View code examples on GitHub
License: MIT

1. Thinking of the Web

This workshop will leave you with the ability to create your own website. Not only will we teach you how to code, but we'll be covering some of the tools and thought processes you may use to design and create content for your website.

Before we write a line of code, let's think a little bit about what you'd want your website to achieve.

1.1 The Purpose of the Web

The initial purpose of the "world wide web" was to distribute information. A web of interconnected documents that made all human knowledgeable accessible simply by clicking.

Since its inception, the web has expanded to do a lot more than that. Nowadays we can write documents, order food, play games and more on the web but its primary purpose is still as strong as ever.

In this workshop we'll cover the purpose of distributing information, by trying to make a website that does exactly that. It will, however, give you a springboard to explore all those other things the web can do nowadays.

It will help to be aware and critical when visiting websites. Does a website let you do what you want to quickly? Does it make you angry? Does it look good? Why do you think it does this? This will help you to steal good ideas and avoid the mistakes of others.

1.2 Design Before Building

The most useful thing that you can do before setting out to create your website is deciding what it will be about. Is there a cause you're passionate about, a project you did, or a blog you want to start? If you're struggling for ideas, a personal website is a good place to start. This is like an online CV or a LinkedIn page with a little more personality.

Once you know what you're trying to convey, it can help to think a little bit about what you want it to look like. This will help to keep you focused when creating it, and also give you some real goals to reach when learning how.

You don't need sophisticated tools to do this, pen and paper will do just fine. Sketch out a simple idea and focus on the big details, such as what sections you want, if you want multiple pages and what images could work.

Over the course of this workshop, I will be building a website about web design and showing you how I do it. Here's a design a sketched out design of this.

I'll explain the bits and pieces as we make them, but it's a good place to start. I've taken cues from websites I like, such as this concept of a "hero", which is a section at the start of a website with large text and a colourful background of some sort. Below, you'll see MDN (a website we will return to) has the same.

Task: Decide on a topic for a website you want to create.
Task: Sketch out a rough design of the website, on whatever tool you think suitable.

Now that we've thought a little bit about our goals, we can actually start building something. Let's move onto the first language of the web: HTML.

2. HTML: Displaying Information

2.1 Setting Up

A website is split up into different components that describe the information that is given to you, what that information looks like, and how it can be interactive and dynamic. We do this through three different languages: HTML, CSS and JavaScript respectively. Today we will be focusing on displaying that information through HTML.

Previously we asked you to set up a text editor (check out the setup instructions for details on this). A text editor does exactly what its name describes: gives you the ability to edit text.

Firstly, we want a place for our website to live on our computer. A website is made up of multiple files, so it makes sense for it to have its own folder. Make this folder anywhere on your computer, and give it a name. I'm going to call mine web-design-website. After making the folder, I can open it in the text editor. In Visual Studio Code, this is done through File>Open.

In this folder, you want to create a new file. Call it index.html. We give it the name index by convention, and give it the extension .html because it is an HTML file.

To preview this, open your index.html file in any modern web browser (such as Google Chrome). Usually double clicking on the index.html file does this (File>Open works as well). You should see... nothing!

This is just your browser showing you an empty website. We'll soon fill it with content.

Task: Get a text editor/JSBin ready.
Task: Open a new folder.
Task: Make an empty index.html file.
Task: Open it in your web browser.

2.2 Writing your first HTML

An Aside About Syntax

We said that we were going to learn how to present information. At first, it won't be pretty.

HTML is the language that is used to do this, it stands for HyperText Markup Language. This basically means that it takes ordinary text and gives it meaning by tagging certain parts of it. For every single website you visit, the first thing it does is load an HTML file. Here is an example:

<element attribute="value">
    <selfclosingelement />

You can put the syntax down to a few core aspects:

What was written above actually isn't valid HTML, there is a limited set of elements that exist and they represent different parts of a website - for example there is an element for images and there is one for headings.

Adding Content to the Screen

Now that we are empowered by what HTML looks like, let's edit our index.html file that we made earlier, adding the following HTML code:

<!DOCTYPE html>
        <h1>Web Design Tips</h1>

Once you've added this content, save it, then, refresh your browser. This is crucial for you to see your changes. Everything going well, you should see...

What's going on with this code you just put in? Stepping through it line by line:

  1. This is a "doctype". It betrays the syntax we just introduced, but it lets the browser know that you are writing HTML
  2. This is the first tag of the document, the html tag. All of our HTML goes in here
  3. The body tag opens, inside this tag is everything that the user can see
  4. This is a complete h1 tag, with some text inside it. h1 means the top level heading of a document - there are h2, h3, h4, h5, h6 as well.
  5. Closing of the body tag (never forget to close!)
  6. Closing of the HTML tag

Note: If you want to find out about a tag, or try to do something you don't know how to do, a good place to start is by searching. Google will likely find you the answers you're looking for. MDN Web Docs is also a fantastic resource for all things web.

Task: Add this content to your index.html file.
Task: Give your website a heading that is more fitting for your content.

2.3 Some Basic Tags


The <p> tag is where you put main text. Where you'd usually put two line breaks in your word processor of choice, you're separating paragraphs - this is how you separate paragraphs in HTML

<p>Lorem ipsum dolor sit amet, sonet audiam theophrastus ex vim, mea ei enim liberavisse interpretaris. Ei minimum deserunt vim, quodsi philosophia ea vix. An laudem integre sapientem mei. Legere adipisci mea et, duo dicunt invenire et, mel ad veniam iriure aperiam.</p>

<p>Vel ei ferri praesent. Per id exerci civibus, no commodo numquam ocurreret vim. Ex vim possim everti, mel insolens laboramus ex, mei verear integre eu. Eu epicurei delicatissimi pri, alterum feugiat pertinax ut qui. Ex nec omnes accommodare, eum ut regione incorrupte. An docendi reformidans vix.</p>

Task: Write a few paragraphs on something. For example: introducing yourself and why your website is worth reading. Add some extra h1-6 tags to give it some structure.

Adding Flair

Where would we be if we couldn't emphasise or scream out text? HTML let's you do this with the <em> (emphasis: italics) and <strong> (strong: bold) tags.

This is some text that I am <em>emphasising</em>. I am also making it <strong>strong</strong>.

Task: Let your reader know what is important by emphasising and strengthening some of your content.
Challenge: There are many more tags you can use. Can you find out what <small>, <ul>, <ol> and <table> are for, and put them to use?

2.4 Links

HTML and the web was so exciting when it was first made because you could link to other pages - suddenly everything was interconnected. This is done through the humble <a> tag (for anchor). It specifies where to link to with the href attribute.

This is a link to <a href="">Google</a>.

A word of warning about URLS in html. When you supply a URL to a web browser (e.g., it is resolved in different ways. What this means is that it won't be interpreted exactly as you write it.

Say that you have a page on and there are links to it. There are three different modes:

This means that you cannot just type to link to You have to type out the full URL.

Task: Add some links to your favourite websites.
Challenge: Want your website to have more pages? Try adding another page, (e.g. mypage.html), in the same folder as index.html and linking to it.

2.5 Images

Finding Images

Images help to convey the information you want to. They're easy enough to put in your website. The hardest part is usually finding or creating the right images to use. Unfortunately, you can't legally take most images you see on the web and put it into your website (although you can technically).

However, there are websites that let you access images you can access legally. Pexels is one such website. You can search for images, download them and include them in your website with a clear conscience. For example, after searching for "laptop", I found this image. To get it ready for my website, I want to

Task: Find at least one image to put on your website.

Using Images

Note: All of the rules about URLs specified earlier apply here.

You use the <img> tag to tell the browser to display an image, and the src attribute to specify where that image is on the web. Optionally, you can use the alt attribute to describe the image. This is useful for visually impaired users and search engines who both have a hard time of telling what is in the image.

<img src="desk.jpeg" alt="A desk" />

It's still quite oversized! We'll go over how to make these images behave properly in terms of sizing, later.

Task: Add your image(s) to your website.

2.6 Embedding Other Media

You may want to embed other kinds of media, such as video. There is a <video> tag but sourcing and hosting video is rather difficult. Fortunately, popular hosting websites like YouTube.

Embedding media from these websites is surprisingly easy, they usually have an embed button tucked away somewhere, which gives you a snippet of HTML code. For example, on YouTube it's inside the "share" box.

It gives me an HTML snippet, which I can put in my website.

<iframe width="560" height="315" src="" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

Lots of websites allow for this, such as Twitter and Facebook.

Task: Embed a video into your website.
Challenge: Try embedding another kind of media, such as a tweet or Facebook like button.

2.7 The <head> Tag

Earlier, we introduced you to the body tag. This is everything the user can see on the page. What about other things? You'll notice this ugly "index.html" in your tab bar. Other websites have a useful description of what they are.

We can change this, but not by putting anything on the page. This is done by adding a head tag before your body tag, and putting a title tag in that to set the title of the page.

        <title>Web Design Tips</title>

Much better!

Task: Give your website a title in the head tag.

This is all we have to say on HTML for now. You can see the finished result in the example-01-html folder of the examples repo.

This website has content, but it doesn't look very good. Next we'll be focusing on how to add styles with CSS to make it visually appealing.

3. CSS: Adding Style

At the end of the last section, we left you with a website you could fill with content, but it didn't look particularly nice. CSS is the next language we'll be exploring and it describes what HTML looks like. We call this styling!

3.1 Writing Styles with CSS

Setting Up

CSS code lives in its own file, separate from HTML. Start by making a new file, in the same folder as index.html, called main.css. css because we're making a CSS file, and main, again, by convention.

Fill it with this content, so we can tell that the styles are working - we'll go over exactly what this means later.

body {
  background: blue;

Recall the head element. You put this outside of the body element to group information the user can't see directly on the page. Previously, we put the title of the website in there, as that was something not shown on the page. Declaration of your styles is similar. To tell your browser to use the CSS file, you need to add an HTML tag in your head element.

<link rel="stylesheet" href="main.css" />

The link element is saying "use the file given (main.css) in some way". The rel attribute indicates how the browser should use the file - in this case as a stylesheet. In summary: "use this file I'm giving you to add styles to the bag". Notice the main.css in the href attribute matches the name we gave the file earlier.

Save everything and refresh the page, you should see a beautiful sea of blue.

I know I promised we were going to make the website look better, not worse. We'll get there in a moment.

Task: Add a main.css file with the example snippet above.
Task: Add a link tag to the head element of your index.html. Refresh the page and verify that your website is indeed blue.


CSS syntax is really simple:

selector {
    property1: value1;
    property2: value2;

The selector allows us to select an HTML element (or a group of them) and apply different properties to them using the property: value syntax. These properties vary far and wide and can do a lot of things such as change the colour, size of the text or where the element is located on the page.

Selecting Elements: Your First Styles

There are lots of kinds of selectors. One is the element selector, which applies the style to all elements of the given name. Looking back at the snippet you copied verbatim, we can see what this is doing:

body {
    background: blue;

This applies the style (a blue background) to the body element (everything the user can see).

We can apply more styles to the body, such as changing the colour of the text. This is done with the color property (note the American English spelling).

body {
    background: blue;
    color: white;

At least we can read the text a bit better. But those links down the bottom, they're still pretty hard to see. We can apply a style to all a elements on the page.

a {
    color: yellow;

Task: Colour your background, text and links. Try giving your headings a different colour.

Finally it's time to abandon these awful colours and actually make this look good.

3.2 Making Sense of Colours and Fonts

Some of the easiest steps we can take towards a less visually offensive website is by changing the fonts and colours.

Colours in CSS

Are we restricted to a small set of colour names like blue, yellow, white, etc. ? Not at all! In fact, all browsers treat these colours slightly differently, so we'd be wise to steer away from them if we want more precise results.

You can describe any colour the screen can render in CSS. There are many different ways to do this, but to actually create the colours on the fly requires an understanding of how computers understand colour which isn't strictly necessary for creating websites.

In the above image, you'll see various different representations for the same colour. None of them make intuitive sense if you're not familiar with the format.

It's easier to pick the colours visually, and use the code some software gives you. One tool you can use is Coolors. It can randomly generate entire colour schemes for you, which gives you a selection of colours to choose from.

You can also lock colours in, so when generating new schemes, it keeps the colours you want. In my website, I know I want a bright blue, so I generate new schemes until I see a bright blue. Then I lock it, and generate new schemes. I can also tweak colours with the colour picker. After a while, I turned up with this:

Those "hex strings" at the bottom (like #EF476F) are the colours you can put in CSS. From this scheme, I've decided to allocate different colours to different parts of my website:

With a bit of CSS, I can make this happen

body {
  background: #F2F7F9;
  color: #535982;

h1, h2, h3, h4, h5, h6 {
  color: #8A9E62;

a {
  font-weight: bold;
  color: #5887FF;

Using commas between selectors (h1, h2, h3, h4, h5, h6) allows the selection of multiple elements (all heading elements). font-weight: bold makes the links bold so they stand out a bit.

That's looking a lot better.

Task: With Coolors or otherwise, pick some colours for your website.
Task: Apply some tasteful colours to your website.


The fonts on a website are a large part of its personality.

There are countless fonts to choose from, but they need to be on a user's system for them to be visible on a website. Fortunately, CSS allows websites to download fonts on the fly for use.

Where do we find fonts that we can use for free? Google Fonts is a particularly good resource for this. It lets you browse hundreds of fonts, and easily include any number of them on your website.

You can add fonts that you like the look of by clicking on the plus buttons next to them, and then you're given embed instructions. I like the look of "Muli".

Under the "customize" tab, you can choose the variants of the particular fonts you've chosen. Because I use italics and bold on my website, I've added the "bold" and "italic" variants.

Ready to embed, I go back to the "embed" tab and follow the instructions. "Add the code to your <head> tag". My head now looks like this:

    <title>Web Design Tips</title>
    <link href=",400i,700" rel="stylesheet">
    <link rel="stylesheet" href="main.css" />

And by adding font-family: 'Muli', sans-serif; to my body CSS, my website is transformed once more!

Task: Find a font on Google Fonts that you want to use.
Task: Embed them on your website.
Challenge: You can use different fonts in different places - such as in the headings. Find a different font and use it in different elements on your website.

3.3 Classes: Fine-grained Selectors

We can now target elements and style them, this is great. But what if we just wanted to target one <p> element instead of all of them? For example, I want the introduction paragraph on my website to be slightly bigger. Well, that's where classes come in. We can define a class as an attribute of an element and then select that class in CSS. For example

<p class="introduction-text">Foo bar</p>
.introduction-text {
  font-size: 1.2em;

See the . in front of the selector in the CSS code? That's how to select a class.

em units: We set the font-size of the emphasis paragraph to 1.5em. em units are a relative unit, meaning it depends on the font size of its parent. So by specifying 1.2, we are saying that .introduction-text elements should have a font 1.2 times bigger than its container. There are also rem units (root em), which are in terms of the font size at the root of the website.

Task: Make an important paragraph on your website stand out with classes.
Task: Add some other classes to give your website a little more flavour.

3.4 Layout

We've changed the size and appearance of individual things on the page. Another important part of styling your website is changing how all of the components fit together. We call this layout, as in, how the elements are laid out on the page.

Inline and Block Elements

You've probably already noticed that some elements flow vertically. h1 and p elements all start on their own lines. These are called block elements. They create blocks to fit their content and flow vertically down the page.

Other elements flow with their surrounding text. em and strong do not start new lines. These elements are called inline elements. They fit inline with text and flow horizontally along the page. Except when they reach the end of the line, at this point they flow like words do and wrap to the beginning of the next line. Line breaks can even appear inside inline elements.

A good rule to remember at this point is that it makes sense to put inline elements inside block elements, but you should not put block elements inside inline elements. Later we will explore inline block elements which allow you to do this.

<p><em>This makes sense</em></p>
<em><p>This does not!</p></em>

div and span

Sometimes you want an element that doesn't really have any meaning, just an extra container to apply styles to. p or h1 don't really make sense in this case.

There are elements that have no intrinsic properties other than that they are either inline or block elements. They're like a blank canvas for us to our ideas that don't fit in the pre-defined set of HTML elements. These are span and div which are inline and block elements respectively.

<span>I am an inline element</span>
<div>I am a block element</div>

Let's put one of these to use. The content on our website is much too wide. The text fits the width of the screen and this can get very hard to read.

To fix this, we can create a new class for our content, called main-content.

.main-content {
    width: 600px;
    margin-left: auto;
    margin-right: auto;

Some new CSS properties there, which we will explain in a moment. However, if we wrap our content in this:

<div class="main-content">
    Your website content

We see something that is much easier to read!

That image is still massive. Later on we'll be turning it into that big hero section at the start of the website.

Task: Add some kind of content container to your website to make text more readable.

The Box Model

In the previous section we started adding CSS properties like margin and width. These contribute to the size of an element, and are part of the box model. This is best described with a diagram, courtesy of MDN.

Basically, the size of an element is made up of these four components:

These dimensions can be specified in every direction (left, right, top, bottom).

Try experimenting with the properties using this class:

.box-model-test {
  width: 100px;
  height: 100px;
  margin: 10px;
  padding: 10px;
  border: 2px solid black;
  background: red;

The pixel unit: We've been setting these dimensions in terms of px, which represents one pixel on the screen. Another way of thinking of these is something very, small. A border of width 1px would be a hairline border.

What's the deal with margin: auto? If a block, fixed width element has margin-left and margin-right set to auto, it will centre itself in the middle of the page. Not intuitive, but very useful!

Task: Experiment with the box model properties.
Challenge: Adding a direction to margin, padding, or border makes it only operate in that direction (such as padding-left). Experiment with those properties.
Challenge: Emphasise another area of your website by putting it in a coloured box with some padding.

Making a Button

I want the links at the bottom of my website to stand out a bit more, like the bold buttons I see on other websites. I want to create a new class, button, that I can apply to them to make them stand out a bit more.

Here is the class, with comments added.

/* These are comments, they are here only for you to read
   and don't change the output in any way. */
.button {
    /* Make the element inline block. See below for more explanation. */
    display: inline-block;

    /* Add some padding to keep the text far away from the edges. */
    padding-left: 0.8em;
    padding-right: 0.8em;
    padding-top: 0.4em;
    padding-bottom: 0.4em;

    /* Add some spacing between buttons */
    margin-right: 1em;
    margin-bottom: 1em;

    /* A bright background with light text (replace with your own colour) */
    background: #5887FF;
    color: #F2F7F9;

    /* Make the corners slightly rounded */
    border-radius: 4px;

    /* Links are usually underlined, let's turn that off */
    text-decoration: none;

We added this particular property, display: inline-block. This made each element with the button class an inline block element, which is a combination of inline and block elements. This simply means they flow with text (horizontally, but not across line breaks) and follow the box model like block elements. Inline block elements can contain block elements.

Adding this class to all of the links in the resources section yields a big improvement:

Task: Emphasise some of the links on your website by turning them into buttons.
Challenge: Can you add some more flair to your buttons? Try adding a border or exploring the use of box-shadow. Challenge: Can you emphasise other parts of your website using the box model?

3.5 Pseudo Classes and Transitions

When the mouse hovers over the button, and when we click on it, nothing changes on the button to reflect our interaction.

There are selectors in CSS called pseudo classes, they reflect the particular state that an element is in. For example, if we want to make our buttons lighter when we hover over them and darker when they're pressed (active), we can do that with pseudo classes.

.button:hover {
    background: #91B0FF;

.button:active {
    background: #374e89;

    /* Make the button a little smaller */
    transform: scale(0.9);

But these colour and size changes are quite jolty. Instead of snapping instantly, what if the changes happened over time? There is a CSS property for that, called transition. Adding a declaration in your button class (the main one), will make the changes smooth.

.button {
    /* All of your other CSS 
    /* Changes because of the pseudo classes below should happen over time.
       0.2s means 0.2 seconds. */
    transition: 0.2s;

Now that is smooth!

Task: Make your buttons respond to user input by adding pseudo class selectors.
Task: Make them change smoothly using transition.
Challenge: It is possible to make different properties change at different speed (e.g. the colour fades over 0.2s but the size over 1s). Can you figure out how to do this?

3.6 The Hero

Since the inception of my web design tips website, I've wanted a big bold hero section at the top of the website. I'm finally going to make it.

I'm going to create two classes, one for the image background and one for the text. Firstly, the image background

.hero-container {
    /* Add a lot of padding so we can see a lot of the image */
    padding-top: 150px;
    padding-bottom: 150px;
    padding-left: 20px;
    padding-right: 20px;

    /* Set the background to an image */
    background: url(desk.jpeg);

    /* Make the image cover the entirety of the hero */
    background-size: cover;
    background-position: center;

    /* Put the text in the middle */
    text-align: center;

Then I'm going to remove my h1 and img at the top of my main container, and put this outside of it, at the root of the body tag.

    <div class="hero-container">
        <h1>Web Design Tips</h1>
    <div class="main-content">
        The rest of the website

That's a start! One thing I notice immediately is that ugly white border around the hero. This is default padding that most browsers add to websites. We can remove it fairly easily:

html, body {
    margin: 0;
    padding: 0;

Much better!

Finally, let's do something about the text. I want it to be darker, and be in all caps with a lot of spacing between the letters. CSS lets me do all of those things. I make a new class for the heading.

.hero-heading {
    color: #535982;
    text-transform: uppercase;
    letter-spacing: 0.2em;

    /* Removing any default margins */
    margin: 0;

Then I apply it to the h1 element inside the hero.

And the hero is done!

3.7 Behaving Better on Mobile

A significant portion of users are viewing on a mobile device with a smaller screen. If we look at this website on such a device, we get something less than desirable.

This could be made a lot better. A website that works well on mobile and desktop devices (so a device of any size) is known as a responsive website. Let's make our website responsive.

Firstly, we need to add this tag into the head element.

<meta name="viewport" content="width=device-width, initial-scale=1" />

This basically tells the browser not to scale our website to fit the device, because we'll make everything work on our own.

The text is a normal size now, but it's cut off. This is due to the parts of the website that are a fixed size. There are two of things that are fixed size at the moment:

We'll fix them one at a time. For the main content container, we'll use max-width to make sure it is never wider than the screen.

.main-content {
  /* Be 600px wide, but no wider than the container */
  width: 600px;
  max-width: 100%;

  /* Add some padding for when it is the width of the screen. 
     box-sizing is required to fix a quirk with how width works. */
  padding: 20px;
  box-sizing: border-box;

  /* Centre horizontally */
  margin-left: auto;
  margin-right: auto;

As for the video, making it responsive isn't straight-forward. There's a website, Embed Responsively that gives a responsive embed code for some services (YouTube being one of them). I can use the embed code it gives me in place of the embed code I put in before.

And now, the website behaves on mobile.

Task: Make your website responsive so it can work well on mobile devices.
Challenge: Media queries in CSS allow you to apply different styles at different screen sizes. For example, you could make your text slightly smaller. Can you figure out how to use them?

3.8 Further Reading

We've dramatically improved this website by using CSS. View the final result in the example-02-css folder.

You now have the foundations to start exploring a bunch of different concepts.

Firstly, every website you visit is research. If you see something you like, and want to figure out how it works, most browsers give you the ability to do this. Most of the time, you can right click an element and select something like "inspect". Then you get a panel that gives you information about the HTML and the CSS of the element you selected:

As well as that, here are some links worth exploring:

4. JavaScript: Make it Interactive

So far we've explored how to display information on our webpage using HTML and how to style it using CSS.

At some point, we may want to

Clearly, the technologies at our disposal don't let us do this. This is where JavaScript (often abbreviated as JS) comes in. JavaScript is a programming language. This simply means we can use it to do basically anything a computer is capable of. This is really powerful.

Note: You may hear people talk about JavaScript or just Java. Confusingly, these are two separate and very different programming languages! Calling one of them the other may offend someone. You have been warned.

If you have never programmed before, this section may be confusing. If you find yourself struggling and unable to work through the practical examples, I recommend you try something that dives into the subject a little more comprehensively. Our Introduction to Programming workshop is a great place to do this.

If you are familiar with programming, this section should be very straight-forward.

4.1 Your First Script

Concepts of Programming

Unlike HTML and CSS, I can't demonstrate you a simple example that encompasses all possible syntax in JS. Instead, I give you a metaphor: JavaScript is a series of instructions that the computer will execute one after the other.

To make an example, consider my original website design from section 1. I claimed one of the features I wanted was a colour chooser. Now I can explain exactly what I mean by that. I want a button, that when clicked, gives the user a random colour that they can use in their CSS. It's an inspiration tool.

If my website could understand instructions in plain English, I'd tell it something like this:

whenever the user clicks a button:
  create a random colour
  display this colour to the user

JavaScript is just a series of instructions like these, but one that my website can understand.

Writing a Script

Just like CSS, we're going to make a new file and tell the website how to use it. Create a new file called main.js (main once more by convention, js for "JavaScript"). Fill it with this snippet:

alert('I can write JavaScript');

Now we need to tell the page to use it.

At the end of your <body> element, add this element:

<script type="text/javascript" src="main.js"></script>

You may think this is very counter-intuitive:

For the first two points I can't offer you a satisfying explanation other than "decisions made by people a long time ago". However, the reason it is in the body element is slightly justifiable. In fact, it can go in the head tag and for now it will work. But our script will eventually be modifying elements on the page, which means they have to exist first. When the browser sees the head tag, it hasn't yet seen the body tag and all the elements it contains, so neither can our script.

There are other ways around this, but we will use this one for now.

What you should see, provided everything is working, is this:

An unhelpful popup before the webpage has even loaded.

If we dissect the code a little bit more, we can make some sense of it:

alert('I can write JavaScript');

alert, the thing before the brackets, is what should be done (create an alert popup), and the text in quotes inside the brackets is some extra information. In this case, it represents the text to put in the popup.

This alert function is generally considered bad practice for web developers. It has a whole bunch of undesirable features, but right now it very quickly demonstrated that the script was being loaded and executed. Now, we will delete it, and never write it again.

Task: Create a main.js file and add the example snippet to it.
Task: Refer to the file using a script tag at the end of the body
Task: Check that you see an alert on the page. Can you change the text it displays?
Task: Delete the code in your script and apologise to your browser.

4.2 The Developer Console

Opening the Console

With CSS, we briefly looked at the concept of "inspecting" an element in the browser so we could better understand the code we were writing. What you were opening in actuality was the browser's developer tools in one of its various modes. The developer tools are an invaluable resource and come with many useful features to help you build websites. In the JavaScript world, it is impossible to get by without it.

Your experience will differ browser by browser. We recommend, and will be demonstrating with, Google Chrome for the smoothest development experience.

Firstly, you need to open the developer tools. This varies by browser/OS but it is usually one of the following:

We're not sure about Linux, could someone have a tinker and let us know?

In Safari you will need to enable the Developer Tools by checking the option in Preferences > Advanced > Show Develop Menu first.

Once the developer tools are open, you will have a variety of tabs to choose from. Select the Console tab and you should see something similar to this:

Running Code in the Console

The first use of the console is that you can write JavaScript code directly into it, to see what it does. There's usually a space to write some code, next to a symbol. Write some code (such as your alert snippet from above), and see what happens.

JavaScript can also perform arbitrary mathematics. + - * / mean add, subtract, multiply and divide respectively.

Try entering some expressions into the console and seeing what your browser makes of them.

Printing to Console

One of the most common actions of a developer is to print to some output to make sure things are going smoothly. JS is no exception. Where your unsightly alert was (inside main.js), you can now make a console.log which is far more elegant.

console.log('I am a real web developer');

And you should get a result like this:

Task: Verify that you can open the developer tools and console in your browser
Task: Try to run some JavaScript code directly in the console
Task: Print something to the console from your main.js script using console.log

4.3 Changing Things on the Page with the DOM

We're kind of operating in a vacuum here, we can bring annoying popup windows and print to a hidden console but how do we do something useful? At some point, you'll have to start interacting with, and modifying the HTML on the page.

JS has a well-defined way of doing this, through what is called the DOM (Document Object Model).

This is just a fancy way of saying that we can locate and manipulate every HTML element as a JavaScript object, and have that reflected in our web page.

We can use our browser's console to experiment with this concept. Let's try typing out the following:


The console will spit out an object. That string we passed to it was a CSS selector. This object represents the <h1> element on your page. Some browsers will let you hover over it to very easily see that this is the case. For example in Chrome:

We can manipulate this object now. In your brower console try typing

document.querySelector('h1').innerHTML = 'Dynamically changed heading';

Task: Using the console and document.querySelector, change the contents of some elements.
Challenge: You can also change the values of attributes (such as href for a elements). Can you figure out how to do this?

4.4 Creating the Colour Creator

Now that we understand how to change elements on the page, we can try to make something useful.

Back to this colour selector. I want to generate a random colour on demand, and present it to the user. We'll worry about this "on demand" part later. For now, let's try and create a random colour.

The UI

I'm going to add the following HTML and CSS to my website

<h2>Colour Creator</h2>
<div class="color-creator-box"></div>
.color-creator-box {
    width: 100%;
    padding-top: 120px;
    padding-bottom: 120px;
    background-color: #000;
    color: #fff;
    border-radius: 4px; 
    font-size: 2em;
    text-align: center;

Which looks like the following:

To create new colours:

Creating a Random Colour

One particular form of colours in CSS is called rgb, they look like this (this colour in particular is a light green).

rgb(123, 252, 99)

The important point is that those three numbers can be any number between 0 and 255. All we need to do is generate three random numbers between 0 and 255 and format them like rgb(x,y,z).

How do we do this? With maths!

The code Math.random() in JavaScript will give us a random (decimal) number between 0 and 1 (not including 1). If we multiply it by 256, we get a random (decimal) number between 0 and 256 (not including 256). If we round it down, we get a random whole number between 0 and 255 - exactly what we want. Math.floor(number) gives us the number rounded down. Here's an example

// These are comments in JavaScript. They don't do anything,
// but are useful for us to read!

Math.random() // gives us e.g. 0.32
(Math.random()) * 256 // 0.32 * 256 = 81.92
Math.floor(Math.random() * 256) // 81.92 rounded down = 81

So to create three of these random numbers, we use the expression Math.floor(Math.random() * 256) thre times.

Firstly we create these three numbers and give them names using a let statement. let x = y basically means, every time I ask for x, give me y.

let red = Math.floor(Math.random() * 256);
let green = Math.floor(Math.random() * 256);
let blue = Math.floor(Math.random() * 256);

I used the names red, green and blue because that's what the three numbers actually represent, but that's not so important.

Now we can actually create a string representing the colour. A string is what we originally passed to console.log, it is just text. The neat thing about strings, is when you add them together, it creates a new string with them placed one after the other.

'web' + 'developer' // 'webdeveloper'

So we can create a new string for our colour:

let color = 'rgb(' + red + ',' + green + ',' + blue + ')';

You can check it works by logging it

// This should print something like 'rgb(123,20,40)'

Task: Experiment with randomness in the console. Can you create a random number from 5 to 25?

Applying the Colour

Finally we want to make the box match what we've just created.

// Give this value a nume so we can refer back to it
let colorCreatorBox = document.querySelector('.color-creator-box');

// .style lets us modify CSS styles directly = color;

// Set the text so the user can copy and paste the colour
colorCreatorBox.innerHTML = color;

Task: Use JavaScript to add some interesting, dynamic behaviour to your page.

4.5 Events and Interactivity

Currently the colour is set every time we load the page. I would like a way to change the colour on the click of a button. I want to add a way for the user to interact with my website in a richer way.

Events are precisely the way to do this. Every time the user interacts with an HTML element in some way (for example, clicking on it), it will emit an event. We can attach some code to this event to be run every time the event is emitted.

TLDR; we can make code happen when someone clicks on something.

Adding the UI: A Button

I'm going to add the following HTML just above the creator box:

<button>Create a new colour</button>

The <button> element is what it sounds like, something that can be clicked on.

That's a wee bit ugly, let's add our button class to it.

<button class="button">Create a new colour</button>

Something doesn't look right here! The button looks different from the other buttons. This is because button elements have some default styles that we need to override. So we add the following to our button CSS class:

font-family: inherit;
font-size: inherit;
font-weight: bold;
border: 0;
cursor: pointer;

Look up the properties and values if you're interested in exactly what they mean.

This is looking much better.

Finally, we add a new class, color-changer-button, so we can target this element specifically in JavaScript.

<button class="button color-changer-button">Create a new colour</button>

Task: Add a button to your page, and make it match the other buttons on your website.

Making Code Re-Usable with Functions

Because we want code to be run every time something is clicked, it isn't sufficient to run it once. We need to wrap it up so we can run it on demand.

This is what functions in JavaScript are for, they let you wrap up pieces of code to re-run them at any time. You've used them already: alert, console.log and document.querySelector are all functions.

Here's the code for creating the new colour:

let red = Math.floor(Math.random() * 255);
let green = Math.floor(Math.random() * 255);
let blue = Math.floor(Math.random() * 255);

let color = 'rgb(' + red + ',' + green + ',' + blue + ')';

let colorCreatorBox = document.querySelector('.color-creator-box'); = color;
colorCreatorBox.innerHTML = color;

Instead, we can wrap it in a function:

let colorCreatorBox = document.querySelector('.color-creator-box');

function createNewColor() {
    let red = Math.floor(Math.random() * 255);
    let green = Math.floor(Math.random() * 255);
    let blue = Math.floor(Math.random() * 255);

    let color = 'rgb(' + red + ',' + green + ',' + blue + ')'; = color;
    colorCreatorBox.innerHTML = color;

We don't put let colorCreatorBox = ... in the function because this value will be the same every time the function is run. No point doing it every time.

You'll notice if you run the page now, nothing will happen, because this code has been saved for later use.

If you then run that function, by on a later line writing


You'll see the colour box change! In fact, you can run it in the console directly.

Task: Make some of your code reusable by putting it in a function.


We want this code to be run every time the button is clicked.

let colorCreatorButton = document.querySelector('.color-creator-button');

colorCreatorButton.addEventListener('click', createNewColor);

The magic is in that addEventListener part. This is saying, every time this thing happens (clicking in this case), execute the function I've given you.

Finally, we add a transition to the box.

.color-creator-box {
    /* all the other styles */

    transition: 0.2s;


Task: Use events to make something happen on your website when someone clicks on something.

4.6 Another Example: Big Text Checker

Here's a new feature I want to add to my website. A big text checker. You type in text, and it shows you what it looks like big. Here's a demonstration.

We won't walk through how to create this, you can instead read the code directly from the examples. See if you can make sense of it!

What if we were to put HTML into that box?

My website appears to accept it without a problem. Is this fine?

Let's consider this snippet of HTML:

<meta htttp-equiv="refresh" content="0;url=" />

It's basically saying, take me to straight away. What happens when we type it in?

Eep! It actually does it. Consider this when you're accepting user inputs - people can break your things in unexpected ways. There are solutions, but they require a deeper understanding of how all of this works.

4.7 Further Reading

We've finished adding some dynamic and interactive behaviour to the website. If you want to see the finished result, check out the example-03-javascript folder.

JavaScript can do a lot more. You can build entire web applications or even computer games. Here are some places to jump to if you're interested to know more:

5. Publishing your website

Now we've created a website that we're happy with, we want people to be able to view it. Publishing a website allows people to go to a URL (e.g. and view it. There are lots of ways to publish websites, but we're going to focus on one easy service called Netlify.

5.1 Publishing on Netlify

Head over to Netlify and log in or create an account. You should be presented with a simple dashboard.

You can then drag the folder representing with your website files and it will publish it.

You can see it gives you a rather random name. You can change it in the settings to a name of your choosing.

Then you can follow the link you're given (e.g, and you will see your website in front of you.

You can give this link to other people and they will be able to view your website as well.

Task: Publish your website using Netlify

5.2 Domain Name

One thing you may want is your own domain name. So instead of going to, you can go to The Netlify page for your website has a big "step 2" explaining how to do this. You will need to buy a domain name.

5.3 Finished!

Congratulations! We've created a website from nothing. We've learned how to display information with HTML, style it with CSS, add new behaviour with JavaScript and then publish it for the world to access.

There is so much more you can do with the web. The best way to learn is by doing. Why not jump into one of those further reading links in the previous sections and learn something new?

Further reading