agent-skills/skills/vueuse-functions/references/useScroll.md

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useScroll

Reactive scroll position and state.

Usage

<script setup lang="ts">
import { useScroll } from '@vueuse/core'
import { useTemplateRef } from 'vue'

const el = useTemplateRef('el')
const { x, y, isScrolling, arrivedState, directions } = useScroll(el)
</script>

<template>
  <div ref="el" />
</template>

With offsets

import { useScroll } from '@vueuse/core'
// ---cut---
const { x, y, isScrolling, arrivedState, directions } = useScroll(el, {
  offset: { top: 30, bottom: 30, right: 30, left: 30 },
})

Setting scroll position

Set the x and y values to make the element scroll to that position.

<script setup lang="ts">
import { useScroll } from '@vueuse/core'
import { useTemplateRef } from 'vue'

const el = useTemplateRef('el')
const { x, y } = useScroll(el)
</script>

<template>
  <div ref="el" />
  <button @click="x += 10">
    Scroll right 10px
  </button>
  <button @click="y += 10">
    Scroll down 10px
  </button>
</template>

Smooth scrolling

Set behavior: smooth to enable smooth scrolling. The behavior option defaults to auto, which means no smooth scrolling. See the behavior option on window.scrollTo() for more information.

import { useScroll } from '@vueuse/core'
import { useTemplateRef } from 'vue'

const el = useTemplateRef('el')
const { x, y } = useScroll(el, { behavior: 'smooth' })

// Or as a `ref`:
const smooth = ref(false)
const behavior = computed(() => smooth.value ? 'smooth' : 'auto')
const { x, y } = useScroll(el, { behavior })

Recalculate scroll state

You can call the measure() method to manually update the scroll position and arrivedState at any time.

This is useful, for example, after dynamic content changes or when you want to recalculate the scroll state outside of scroll events.

import { useScroll } from '@vueuse/core'
import { nextTick, onMounted, useTemplateRef, watch } from 'vue'

const el = useTemplateRef('el')
const reactiveValue = shallowRef(false)

const { measure } = useScroll(el)

// In a watcher
watch(reactiveValue, () => {
  measure()
})

// Or inside any function
function updateScrollState() {
  // ...some logic
  nextTick(() => {
    measure()
  })
}

Note

it's recommended to call measure() inside nextTick(), to ensure the DOM is updated first. The scroll state is initialized automatically onMount. You only need to call measure() manually if you want to recalculate the state after some dynamic changes.

Directive Usage

<script setup lang="ts">
import type { UseScrollReturn } from '@vueuse/core'
import { vScroll } from '@vueuse/components'

const data = ref([1, 2, 3, 4, 5, 6])

function onScroll(state: UseScrollReturn) {
  console.log(state) // {x, y, isScrolling, arrivedState, directions}
}
</script>

<template>
  <div v-scroll="onScroll">
    <div v-for="item in data" :key="item">
      {{ item }}
    </div>
  </div>

  <!-- with options -->
  <div v-scroll="[onScroll, { throttle: 10 }]">
    <div v-for="item in data" :key="item">
      {{ item }}
    </div>
  </div>
</template>

Type Declarations

export interface UseScrollOptions extends ConfigurableWindow {
  /**
   * Throttle time for scroll event, it’s disabled by default.
   *
   * @default 0
   */
  throttle?: number
  /**
   * The check time when scrolling ends.
   * This configuration will be setting to (throttle + idle) when the `throttle` is configured.
   *
   * @default 200
   */
  idle?: number
  /**
   * Offset arrived states by x pixels
   *
   */
  offset?: {
    left?: number
    right?: number
    top?: number
    bottom?: number
  }
  /**
   * Use MutationObserver to monitor specific DOM changes,
   * such as attribute modifications, child node additions or removals, or subtree changes.
   * @default { mutation: boolean }
   */
  observe?:
    | boolean
    | {
        mutation?: boolean
      }
  /**
   * Trigger it when scrolling.
   *
   */
  onScroll?: (e: Event) => void
  /**
   * Trigger it when scrolling ends.
   *
   */
  onStop?: (e: Event) => void
  /**
   * Listener options for scroll event.
   *
   * @default {capture: false, passive: true}
   */
  eventListenerOptions?: boolean | AddEventListenerOptions
  /**
   * Optionally specify a scroll behavior of `auto` (default, not smooth scrolling) or
   * `smooth` (for smooth scrolling) which takes effect when changing the `x` or `y` refs.
   *
   * @default 'auto'
   */
  behavior?: MaybeRefOrGetter<ScrollBehavior>
  /**
   * On error callback
   *
   * Default log error to `console.error`
   */
  onError?: (error: unknown) => void
}
/**
 * Reactive scroll.
 *
 * @see https://vueuse.org/useScroll
 * @param element
 * @param options
 */
export declare function useScroll(
  element: MaybeRefOrGetter<
    HTMLElement | SVGElement | Window | Document | null | undefined
  >,
  options?: UseScrollOptions,
): {
  x: WritableComputedRef<number, number>
  y: WritableComputedRef<number, number>
  isScrolling: ShallowRef<boolean, boolean>
  arrivedState: {
    left: boolean
    right: boolean
    top: boolean
    bottom: boolean
  }
  directions: {
    left: boolean
    right: boolean
    top: boolean
    bottom: boolean
  }
  measure(): void
}
export type UseScrollReturn = ReturnType<typeof useScroll>