focus-svelte

Focus lock for svelte with zero dependencies.

Installation

npm install -D focus-svelte
# yarn add -D focus-svelte
# pnpm install -D focus-svelte

Example

https://svelte.dev/repl/4b31b2f4a45c4ee08230f6d47d31db48

Explanation

tabindex

focus-svelte works a bit differently than other focus locks I've encounted. Rather than using an event listener to track user activity and overriding the default behavior of the browser, the DOM is manipulated instead. All elements outside of an active focus lock's descendants or ancestory have their tabindex set to -1 if it was 0 or greater previously.

To keep track of changes after the lock is enabled, a MutationObserver monitors the DOM for updates. Once all focus locks are disabled or removed, the MutationObserver is stopped and the elements' properties are reset. If a focus lock later becomes active, the MutationObserver is restarted and nodes are decorated accordingly.

aria-hidden

If assignAriaHidden is true (default: false), when a focus lock becomes enabled, all elements outside of an active lock or their ancestory have their aria-hidden attribute set to "true".

Usage

There is both an action and a component that can be utilized.

action

<script>
    import { focus } from "focus-svelte";
    let enabled = true;
    function toggleFocus() {
        enabled = !enabled;
    }
</script>

<button on:click="{toggleFocus}">{enabled ? "disable" : "enable"} focus</button>

<div use:focus="{enabled}">
    <input value={enabled ? "focus is locked here" : "regular tabbable input"} />
</div>

<input value={enabled ? "can't tab here" : "can be tabbed into!"} />

With assignAriaHidden

<script>
    import { focus } from "focus-svelte";
    let enabled = true;
    function toggleFocus() {
        enabled = !enabled;
    }
</script>

<button on:click="{toggleFocus}">{enabled ? "disable" : "enable"} focus</button>

<div use:focus="{{enabled, assignAriaHidden: true}}">
    <input value={enabled ? "focus is locked here" : "regular tabbable input"} />
</div>

<input value={enabled ? "can't tab here" : "can be tabbed into!"} />

component

<script>
    import { Focus } from "focus-svelte";
    let enabled = true;
    function toggleFocus() {
        enabled = !enabled;
    }
</script>

<button on:click="{toggleFocus}">{enabled ? "disable" : "enable"} focus</button>

<Focus {enabled} assignAriaHidden="{true}">
    <input value={enabled ? "focus is locked here" : "regular tabbable input"} />
</Focus>

<input value={enabled ? "can't tab here" : "can be tabbed into!"} />

Note: As the action needs an HTMLElement, the component version wraps your content within a div.

override

If you wish to override the behavior of an element, you can set data-focus-override="true" and it will retain its original tabindex.

Contributing

Pull requests are always welcome.

License

MIT