🛠 Off-canvas menu: Building an off-canvas menu

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🛠 Off-canvas menu: Building an off-canvas menu

Starter Source

You’ll learn to build an off-canvas menu in this lesson. The off-canvas menu looks like this:

The Offcanvas menu.

Quick note on Terminology

I will be using the <element> to mean HTML elements. I will also use .class to an element that contains a class.

Examples:

  • <body>: Means the body element
  • .testing: Means the element with the testing class. It also mean the testing class itself

Let’s begin building the component.

HTML for the off-canvas menu

An off-canvas menu is a menu that is placed outside the screen (or the canvas). It looks like this:

Off-canvas menu is placed outside the visible viewport

The HTML for this off-canvas menu will be:

<div class="offsite-container">
  <nav class="nav"><!-- ... --></nav>
</div>

<div class="site-container">
  <button>
    <span>Menu</span>
  </button>
  <!-- ... -->
</div>

Making it work

To make this menu work, you need to push the website to the right when a user clicks the button for the first time.

When the user clicks the button for a second time, you push the website back to the left.

In short, you need to:

  1. Add an event listener to the button.
  2. Push screen to the right when button gets clicked.
  3. Push screen back when button gets clicked again.

Adding the event listener

First, we need to select the button with JavaScript. We can do this with querySelector.

const button = document.querySelector('button')

Then, we add an event listener with addEventListener.

button.addEventListener('click', event => {
  console.log('push the screen!')
})

Pushing the screen

To push the screen to the right, we need to push BOTH .offsite-container and .site-container to the right. The best way to push stuff around in CSS is to use the transform property.

.offsite-container,
.site-container {
  transform: translateX(14rem);
}
Push containers to the right to reveal the menu

We don’t want to push the containers when the website gets loaded. We only want to push the containers when the button is clicked.

The easiest way to tell whether the menu should be open is to add a class to <body>. If the class is present, we need to open the menu. Let’s call this class offsite-is-open.

Your CSS should become:

.offsite-is-open .offsite-container,
.offsite-is-open .site-container {
  transform: translateX(14rem);
}

To open the menu, you can add offsite-is-open to <body> when the button gets clicked.

const button = document.querySelector('button')
const body = document.body

button.addEventListener('click', event => {
  body.classList.add('offsite-is-open')
})
Opening the off-canvas menu

Pushing the containers back

When the button gets clicked for the second time, you want to push the screen back to the left. To do this, you remove offsite-is-open from <body>.

Here’s how to do it:

  1. Check whether <body> has the offsite-is-open class.
  2. If it has the class, remove the class.
  3. If it does not have the class, add the class.

We can check whether <body> has offsite-is-open with an if statement.

button.addEventListener('click', event => {
  if (body.classList.contains('offsite-is-open')) {
    // Remove .offsite-is-open to close the menu
  } else {
    // Add .offsite-is-open to open the menu
  }
})

We can then add/remove the class with classList.add and classList.remove.

button.addEventListener('click', event => {
  if (body.classList.contains('offsite-is-open')) {
    body.classList.remove('offsite-is-open')
  } else {
    body.classList.add('offsite-is-open')
  }
})
Opening and closing the Offcanvas menu.

Here’s a simpler way. You can use classList.toggle to do the same thing as above.

button.addEventListener('click', event => {
  body.classList.toggle('offsite-is-open')
})
Opening and closing the Offcanvas menu with classList.toggle.

🙃.

Wrapping up

If you are thinking “WHAT?! JavaScript can be this easy?”, you’re right. JavaScript can be pretty easy once you know what to watch out for.

But it can be difficult too. You have much more to learn.

Take it slow. We’ll work through everything you need to learn to become a good JavaScript developer.

Exercise

Create the off-canvas menu on your own. You should be able to create it without referring back to this lesson.