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Version: 4.x

fsForesight

[fsForesight] is the simplest way to add predictive callbacks to an Angular app. Put it on an element, give it a callback or an options object, and it registers, updates, and unregisters the element for you.

Import the directive​

ForesightDirective is standalone, so import it directly in the component that uses it:

import { Component } from "@angular/core"
import { ForesightDirective } from "@foresightjs/angular"

@Component({
  standalone: true,
  imports: [ForesightDirective],
  template: `<button [fsForesight]="prefetch">Prefetch</button>`,
})
export class ExampleComponent {
  readonly prefetch = () => {
    void fetch("/api/example")
  }
}

Callback shorthand​

<button [fsForesight]="handlePrefetch">Hover to prefetch</button>

The callback receives the element's ForesightElementState.

With options​

For more control, pass any registration options:

<button
  [fsForesight]="{
    callback: handlePrefetch,
    hitSlop: { top: 20, bottom: 20, left: 20, right: 20 },
    name: 'button-with-options',
    reactivateAfter: 3000,
    enabled: isEnabled()
  }"
>
  Hover to prefetch
</button>

If the bound value changes, the directive updates the existing registration in place. Each options object describes the full configuration, so omitted fields reset to their defaults.

Individual inputs​

You can also pass common options through inputs:

<a
  href="/docs"
  [fsForesight]="prefetchDocs"
  fsForesightName="docs-link"
  [fsForesightHitSlop]="40"
  [fsForesightMeta]="{ route: '/docs' }"
  [fsForesightReactivateAfter]="300000"
  [fsForesightEnabled]="isDocsEnabled()"
>
  Docs
</a>

Defined individual inputs override the matching fields in the options object. If you need a native name attribute, use fsForesightName for the Foresight debug name.

Reading state​

The directive exports itself as foresight:

<button [fsForesight]="prefetch" #foresight="foresight">
  {{ foresight.state().isCallbackRunning ? "Prefetching" : "Checkout" }}
</button>

state is an Angular signal containing the latest immutable ForesightElementState.