prefetch

<drab-prefetch prerender>
    <a data-trigger href="/">Hover to prefetch</a>
</drab-prefetch>

<!-- 
    Alternatively, prefetch all links that with an href that starts with "/". 
    Wrap all of your anchors with the element and use a `trigger` selector.
-->
<!-- 
    <drab-prefetch trigger="a[href^='/']">
        ...
        <a href="/">Prefetch based on trigger selector</a>
        ...
    </drab-prefetch> 
-->

<!-- Prefetch a `url` without providing a trigger. -->
<!-- <drab-prefetch url="/"></drab-prefetch> -->

Overview

The Prefetch element can prefetch a url, or enhance the HTMLAnchorElement by loading the HTML for a page before it is navigated to. This element speeds up the navigation for multi-page applications (MPAs).

If you are using a framework that already has a prefetch feature or uses a client side router, it is best to use the framework’s feature instead of this element to ensure prefetching is working in accordance with the router.

strategy

Set the strategy attribute to specify the when the prefetch will take place.

"hover" - (default) After mouseover, focus, or touchstart for > 200ms
"visible" - Uses an intersection observer to prefetch when the anchor is within the viewport.
"load" - Immediately prefetches when the element is loaded, use carefully.

prerender

Use the prerender attribute to use the Speculation Rules API when supported to prerender on the client. This allows you to run client side JavaScript in advance instead of only fetching the HTML.

Browsers that do not support will still use <link rel="prefetch"> instead.

Speculation Rules Reference

url

Add a url attribute to immediately prefetch a url without having to provide (or in addition to) trigger anchor elements.

This element can be deprecated once the Speculation Rules API is supported across browsers. The API will be able to prefetch assets in a similar way with the source: "document" and eagerness features, and will work without JavaScript.

Extends

Base

Constructors

new Prefetch()

new Prefetch(): Prefetch

Properties

#listenerController

private #listenerController: AbortController

To clean up event listeners added to document when the element is removed.

Inherited from

Base.#listenerController

Source

src/package/base/index.ts:17

#prefetchedUrls

private #prefetchedUrls: string[] = []

Source

src/package/prefetch/index.ts:78

Accessors

#prerender

get private #prerender(): boolean

Prerender with the Speculation Rules API.

Returns

boolean

Source

src/package/prefetch/index.ts:90

#strategy

get private #strategy(): Strategy

When to prefetch the url.

Returns

Strategy

Source

src/package/prefetch/index.ts:85

#url

get private #url(): null | string

url to prefetch on mount.

Returns

null | string

Source

src/package/prefetch/index.ts:95

event

get event(): keyof HTMLElementEventMap

Event for the trigger to execute.

For example, set to "mouseover" to execute the event when the user hovers the mouse over the trigger, instead of when they click it.

Default

"click";

set event(value): void

Parameters

• value: keyof HTMLElementEventMap

Returns

keyof HTMLElementEventMap

Source

src/package/base/index.ts:30

Methods

appendTag()

appendTag(options): void

Appends <link rel="prefetch"> or <script type="speculationrules"> to the head of the document.

Parameters

• options

Configuration options.

• options.prerender?: boolean

Uses the Speculation Rules API when supported to prerender on the client.

• options.url: string

url to prefetch.

Returns

void

Source

src/package/prefetch/index.ts:104

connectedCallback()

connectedCallback(): void

Called when custom element is added to the page.

Returns

void

Inherited from

Base.connectedCallback

Source

src/package/base/index.ts:155

destroy()

destroy(): void

Passed into disconnectedCallback, since Base needs to run disconnectedCallback as well. It is overridden in each element that needs to run disconnectedCallback.

Returns

void

Inherited from

Base.destroy

Source

src/package/base/index.ts:162

disconnectedCallback()

disconnectedCallback(): void

Called when custom element is removed from the page.

Returns

void

Inherited from

Base.disconnectedCallback

Source

src/package/base/index.ts:167

getContent()

getContent<T>(instance): T

Type parameters

• T extends HTMLElement = HTMLElement

Parameters

• instance= undefined

The instance of the desired element, ex: HTMLDialogElement. Defaults to HTMLElement.

Returns

T

The element that matches the content selector.

Inherited from

Base.getContent

Default

this.querySelector("[data-content]");

Source

src/package/base/index.ts:55

getTrigger()

getTrigger<T>(): NodeListOf<T>

Type parameters

• T extends HTMLElement = HTMLElement

Returns

NodeListOf<T>

All of the elements that match the trigger selector.

Inherited from

Base.getTrigger

Default

this.querySelectorAll("[data-trigger]");

Source

src/package/base/index.ts:42

mount()

mount(): void

Passed into queueMicrotask in connectedCallback. It is overridden in each component that needs to run connectedCallback.

The reason for this is to make these elements work better with frameworks like Svelte. For SSR this isn’t necessary, but when client side rendering, the HTML within the custom element isn’t available before connectedCallback is called. By waiting until the next microtask, the HTML content is available—then for example, listeners can be attached to elements inside.