Scrollmus

Framework-agnostic scrollspy script, fork of Gumshoe by cferdinandi. The latest compiled release can be found in the dist directory.

What's different?

• Added useLast toggle GS#128
• Merged GS#111 & GS#117
• Removed polyfill support (Internet Explorer)

Browser Support

Scrollmus supports all modern browsers; this does not include Internet Explorer.

Firefox	Chrome	Edge	Safari	IE
35+	41+	15+	9+	--

Include

Static

Download the latest compiled release from the dist directory.

<script defer src="/path/to/scrollmus.min.js"></script>

Hugo

Scrollmus can be loaded as a Hugo Module.

Initialize the Hugo project as a Hugo Module. Replace the path with your repository.

hugo mod init gitlab.com/username/project

Add the following [module] configuration to the project's config.toml file. If the gitlab.com import fails for your project, replace it with github.com. Scrollmus is distributed on both platforms.

[module]
  [[module.imports]]
    path = 'gitlab.com/aao-fyi/scrollmus'
  [[module.imports.mounts]]
    source = 'dist/'
    target = 'assets/js/scrollmus/'

Load Scrollmus wherever necessary.

{{ $scrollmus := resources.Get "js/scrollmus/scrollmus.min.js" }}
<script defer src="{{ $scrollmus.RelPermalink }}"></script>

Optionally use subresource integrity.

{{ $scrollmus := resources.Get "js/scrollmus/scrollmus.min.js" }}
{{ $scrollmusSRI := $scrollmus | resources.Fingerprint "sha384" }}
<script defer src="{{ $scrollmusSRI.RelPermalink }}" integrity="{{ $scrollmusSRI.Data.Integrity }}"></script>

NPM

The wombats of the group can use NPM.

npm install scrollmus

Usage

The only thing Scrollmus needs to work is a list of anchor links. They can be ordered or unordered, inline or unstyled, or even nested.

<ul id="my-awesome-nav">
	<li><a href="#eenie">Eenie</a></li>
	<li><a href="#meenie">Meenie</a></li>
	<li><a href="#miney">Miney</a></li>
	<li><a href="#mo">Mo</a></li>
</ul>

In the footer of your page, after the include, initialize Scrollmus by passing in a selector for the navigation links that should be detected as the user scrolls.

<script>
	var spy = new Scrollmus('#my-awesome-nav a');
</script>

Styling

Scrollmus adds the .active class to the list item (<li></li>) and content for the active link, but does not include any styling.

Add styles to your CSS as desired. And that's it, you're done. Nice work!

#my-awesome-nav li.active a {
	font-weight: bold;
}

Note: you can customize the class names with user options.

API

Scrollmus includes smart defaults and works right out of the box. But if you want to customize things, it also has a robust API that provides multiple ways for you to adjust the default options and settings.

Options and Settings

You can pass options into Scrollmus when instantiating.

var spy = new Scrollmus('#my-awesome-nav a', {

	// Active classes
	navClass: 'active', // applied to the nav list item
	contentClass: 'active', // applied to the content

	// Nested navigation
	nested: false, // if true, add classes to parents of active link
	nestedClass: 'active', // applied to the parent items

	// Offset & reflow
	offset: 0, // how far from the top of the page to activate a content area
	reflow: false, // if true, listen for reflows

	// Event support
	events: true, // if true, emit custom events

	// End of page
	useLast: true // if true, the last page item will be set as 'active' when scrolled to bottom
});

Custom Events

Scrollmus emits two custom events:

• scrollmusActivate is emitted when a link is activated.
• scrollmusDeactivate is emitted when a link is deactivated.

Both events are emitted on the list item and bubble up. You can listen for them with the addEventListener() method. The event.detail object includes the link and content elements, and the settings for the current instantiation.

// Listen for activate events
document.addEventListener('scrollmusActivate', function (event) {

	// The list item
	var li = event.target;

	// The link
	var link = event.detail.link;

	// The content
	var content = event.detail.content;

}, false);

Methods

Scrollmus also exposes several public methods.

setup()

Setups all of the calculations Scrollmus needs behind-the-scenes. If you dynamically add navigation items to the DOM after Scrollmus is instantiated, you can run this method to update the calculations.

var spy = new Scrollmus('#my-awesome-nav a');
spy.setup();

detect()

Activate the navigation link that's content is currently in the viewport.

var spy = new Scrollmus('#my-awesome-nav a');
spy.detect();

destroy()

Destroy the current instance of Scrollmus.

var spy = new Scrollmus('#my-awesome-nav a');
spy.destroy();

Examples

Nested Navigation

If you have a nested navigation menu with multiple levels, Scrollmus can also apply an .active class to the parent list items of the currently active link.

<ul id="my-awesome-nav">
	<li><a href="#eenie">Eenie</a></li>
	<li>
		<a href="#meenie">Meenie</a>
		<ul>
			<li><a href="#hickory">Hickory</a></li>
			<li><a href="#dickory">Dickory</a></li>
			<li><a href="#doc">Doc</a></li>
		</ul>
	</li>
	<li><a href="#miney">Miney</a></li>
	<li><a href="#mo">Mo</a></li>
</ul>

Set nested to true when initializing. This class name can also be customized.

var spy = new Scrollmus('#my-awesome-nav a', {
	nested: true,
	nestedClass: 'active-parent'
});

Catching Reflows

If the content that's linked to by your navigation has different layouts at different viewports, Scrollmus will need to detect these changes and update some calculations behind-the-scenes.

Set reflow to true to enable this (it's off by default).

var spy = new Scrollmus('#my-awesome-nav a', {
	reflow: true
});

Fixed Headers

If you have a fixed header on your page, you may want to offset when a piece of content is considered "active."

The offset user setting accepts either a number, or a function that returns a number. If you need to dynamically calculate dimensions, a function is the preferred method.

Here's an example that automatically calculates a header's height and offsets by that amount.

// Get the header
var header = document.querySelector('#my-header');

// Initialize Scrollmus
var spy = new Scrollmus('#my-awesome-nav a', {
	offset: function () {
		return header.getBoundingClientRect().height;
	}
});

Use Last Item

By default, when the user scrolls to the bottom of the page the last item will be marked active. To prevent this behavior, set useLast to false when you call Scrollmus. When useLast is false, the item at the top of the page will continue to be marked active.

var spy = new Scrollmus('#my-awesome-nav a', {
	useLast: false
});

Issues

Open new issues in the GitLab Issue Tracker.

License

Scrollmus is distributed under the MIT License.