prefetch

import "drab/prefetch/define";

html

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

<!-- Wrap anchors and use a `trigger` selector. -->
<div>
	<drab-prefetch trigger="a[href^='/']" strategy="visible" prerender>
		<a href="/">Prerender when visible</a>
	</drab-prefetch>
</div>

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

Overview

Defined in: prefetch/index.ts:73

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.

Attributes

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.

Constructors

Constructor

new Prefetch(): Prefetch

Defined in: prefetch/index.ts:76

Returns

Prefetch

Overrides

Lifecycle(Trigger()).constructor

Accessors

event

Get Signature

get event(): keyof HTMLElementEventMap

Defined in: base/index.ts:120

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";

Returns

keyof HTMLElementEventMap

Set Signature

set event(value): void

Defined in: base/index.ts:126

Parameters

value

keyof HTMLElementEventMap

Returns

void

Inherited from

Lifecycle(Trigger()).event

Methods

connectedCallback()

connectedCallback(): void

Defined in: base/index.ts:76

Called when custom element is added to the page.

Returns

void

Inherited from

Lifecycle(Trigger()).connectedCallback

destroy()

destroy(): void

Defined in: base/index.ts:83

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

Lifecycle(Trigger()).destroy

disconnectedCallback()

disconnectedCallback(): void

Defined in: base/index.ts:86

Called when custom element is removed from the page.

Returns

void

Inherited from

Lifecycle(Trigger()).disconnectedCallback

listener()

Call Signature

listener<T>(listener, options?): void

Defined in: base/index.ts:152

Type Parameters

T

T extends keyof HTMLElementEventMap

Parameters

listener

Listener<T>

Listener to attach to all of the trigger elements.

options?

AddEventListenerOptions

Returns

void

Inherited from

Lifecycle(Trigger()).listener

Call Signature

listener<T>(type, listener, options?): void

Defined in: base/index.ts:161

Type Parameters

T

T extends keyof HTMLElementEventMap

Parameters

type

T

Event type.

listener

Listener<T>

Listener to attach to all of the trigger elements.

options?

AddEventListenerOptions

Returns

void

Inherited from

Lifecycle(Trigger()).listener

mount()

mount(): void

Defined in: prefetch/index.ts:143

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.

Returns

void

Overrides

Lifecycle(Trigger()).mount

prefetch()

prefetch(options): void

Defined in: prefetch/index.ts:101

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

Parameters

options

Configuration options.

prerender?

boolean

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

url

string

url to prefetch.

Returns

void

safeListener()

Call Signature

safeListener<T>(type, listener, element?, options?): void

Defined in: base/index.ts:35

Wrapper around addEventListener that ensures when the element is removed from the DOM, these event listeners are cleaned up.

Type Parameters

T

T extends keyof HTMLElementEventMap

Parameters

type

T

Event listener type - ex: "keydown"

listener

(this, event) => any

Listener to add to the target.

element?

HTMLElement

options?

AddEventListenerOptions

Other options sans signal.

Returns

void

Inherited from

Lifecycle(Trigger()).safeListener

Call Signature

safeListener<T>(type, listener, document, options?): void

Defined in: base/index.ts:41

Wrapper around addEventListener that ensures when the element is removed from the DOM, these event listeners are cleaned up.

Type Parameters

T

T extends keyof DocumentEventMap

Parameters

type

T

Event listener type - ex: "keydown"

listener

(this, event) => any

Listener to add to the target.

document

Document

options?

AddEventListenerOptions

Other options sans signal.

Returns

void

Inherited from

Lifecycle(Trigger()).safeListener

Call Signature

safeListener<T>(type, listener, window, options?): void

Defined in: base/index.ts:47

Wrapper around addEventListener that ensures when the element is removed from the DOM, these event listeners are cleaned up.

triggers<T>(instance): NodeListOf<T>

Defined in: base/index.ts:136

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

Inherited from

Lifecycle(Trigger()).triggers

Call Signature

triggers(): NodeListOf<HTMLElement>

Defined in: base/index.ts:137

Returns

NodeListOf<HTMLElement>

All of the elements that match the trigger selector.

Default

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

Inherited from

Lifecycle(Trigger()).triggers