scrollspy.js

/**
 * --------------------------------------------------------------------------
 * Bootstrap (v5.1.3): scrollspy.js
 * Licensed under MIT (https://github.com/twbs/bootstrap/blob/main/LICENSE)
 * --------------------------------------------------------------------------
 */

import { defineJQueryPlugin, getElement, getSelectorFromElement } from './util/index'
import EventHandler from './dom/event-handler'
import Manipulator from './dom/manipulator'
import SelectorEngine from './dom/selector-engine'
import BaseComponent from './base-component'

/**
 * Constants
 */

const NAME = 'scrollspy'
const DATA_KEY = 'bs.scrollspy'
const EVENT_KEY = `.${DATA_KEY}`
const DATA_API_KEY = '.data-api'

const EVENT_ACTIVATE = `activate${EVENT_KEY}`
const EVENT_SCROLL = `scroll${EVENT_KEY}`
const EVENT_LOAD_DATA_API = `load${EVENT_KEY}${DATA_API_KEY}`

const CLASS_NAME_DROPDOWN_ITEM = 'dropdown-item'
const CLASS_NAME_ACTIVE = 'active'

const SELECTOR_DATA_SPY = '[data-bs-spy="scroll"]'
const SELECTOR_NAV_LIST_GROUP = '.nav, .list-group'
const SELECTOR_NAV_LINKS = '.nav-link'
const SELECTOR_NAV_ITEMS = '.nav-item'
const SELECTOR_LIST_ITEMS = '.list-group-item'
const SELECTOR_LINK_ITEMS = `${SELECTOR_NAV_LINKS}, ${SELECTOR_LIST_ITEMS}, .${CLASS_NAME_DROPDOWN_ITEM}`
const SELECTOR_DROPDOWN = '.dropdown'
const SELECTOR_DROPDOWN_TOGGLE = '.dropdown-toggle'

const METHOD_OFFSET = 'offset'
const METHOD_POSITION = 'position'

const Default = {
  offset: 10,
  method: 'auto',
  target: ''
}

const DefaultType = {
  offset: 'number',
  method: 'string',
  target: '(string|element)'
}

/**
 * Class definition
 */

class ScrollSpy extends BaseComponent {
  constructor(element, config) {
    super(element, config)
    this._scrollElement = this._element.tagName === 'BODY' ? window : this._element
    this._offsets = []
    this._targets = []
    this._activeTarget = null
    this._scrollHeight = 0

    EventHandler.on(this._scrollElement, EVENT_SCROLL, () => this._process())

    this.refresh()
    this._process()
  }

  // Getters
  static get Default() {
    return Default
  }

  static get DefaultType() {
    return DefaultType
  }

  static get NAME() {
    return NAME
  }

  // Public
  refresh() {
    this._offsets = []
    this._targets = []
    this._scrollHeight = this._getScrollHeight()

    const autoMethod = this._scrollElement === this._scrollElement.window ? METHOD_OFFSET : METHOD_POSITION
    const offsetMethod = this._config.method === 'auto' ? autoMethod : this._config.method
    const offsetBase = offsetMethod === METHOD_POSITION ? this._getScrollTop() : 0
    const targets = SelectorEngine.find(SELECTOR_LINK_ITEMS, this._config.target)
      .map(element => {
        const targetSelector = getSelectorFromElement(element)
        const target = targetSelector ? SelectorEngine.findOne(targetSelector) : null

        if (!target) {
          return null
        }

        const targetBCR = target.getBoundingClientRect()

        return targetBCR.width || targetBCR.height ?
          [Manipulator[offsetMethod](target).top + offsetBase, targetSelector] :
          null
      })
        .filter(Boolean)
        .sort((a, b) => a[0] - b[0])

    for (const target of targets) {
      this._offsets.push(target[0])
      this._targets.push(target[1])
    }
  }

  dispose() {
    EventHandler.off(this._scrollElement, EVENT_KEY)
    super.dispose()
  }

  // Private

  _configAfterMerge(config) {
    config.target = getElement(config.target) || document.documentElement

    return config
  }

  _getScrollTop() {
    return this._scrollElement === window ?
      this._scrollElement.pageYOffset :
      this._scrollElement.scrollTop
  }

  _getScrollHeight() {
    return this._scrollElement.scrollHeight || Math.max(
      document.body.scrollHeight,
      document.documentElement.scrollHeight
    )
  }

  _getOffsetHeight() {
    return this._scrollElement === window ?
      window.innerHeight :
      this._scrollElement.getBoundingClientRect().height
  }

  _process() {
    const scrollTop = this._getScrollTop() + this._config.offset
    const scrollHeight = this._getScrollHeight()
    const maxScroll = this._config.offset + scrollHeight - this._getOffsetHeight()

    if (this._scrollHeight !== scrollHeight) {
      this.refresh()
    }

    if (scrollTop >= maxScroll) {
      const target = this._targets[this._targets.length - 1]

      if (this._activeTarget !== target) {
        this._activate(target)
      }

      return
    }

    if (this._activeTarget && scrollTop < this._offsets[0] && this._offsets[0] > 0) {
      this._activeTarget = null
      this._clear()
      return
    }

    for (const i of this._offsets.keys()) {
      const isActiveTarget = this._activeTarget !== this._targets[i] &&
          scrollTop >= this._offsets[i] &&
          (typeof this._offsets[i + 1] === 'undefined' || scrollTop < this._offsets[i + 1])

      if (isActiveTarget) {
        this._activate(this._targets[i])
      }
    }
  }

  _activate(target) {
    this._activeTarget = target

    this._clear()

    const queries = SELECTOR_LINK_ITEMS.split(',')
      .map(selector => `${selector}[data-bs-target="${target}"],${selector}[href="${target}"]`)

    const link = SelectorEngine.findOne(queries.join(','), this._config.target)

    link.classList.add(CLASS_NAME_ACTIVE)
    if (link.classList.contains(CLASS_NAME_DROPDOWN_ITEM)) {
      SelectorEngine.findOne(SELECTOR_DROPDOWN_TOGGLE, link.closest(SELECTOR_DROPDOWN))
        .classList.add(CLASS_NAME_ACTIVE)
    } else {
      for (const listGroup of SelectorEngine.parents(link, SELECTOR_NAV_LIST_GROUP)) {
        // Set triggered links parents as active
        // With both <ul> and <nav> markup a parent is the previous sibling of any nav ancestor
        for (const item of SelectorEngine.prev(listGroup, `${SELECTOR_NAV_LINKS}, ${SELECTOR_LIST_ITEMS}`)) {
          item.classList.add(CLASS_NAME_ACTIVE)
        }

        // Handle special case when .nav-link is inside .nav-item
        for (const navItem of SelectorEngine.prev(listGroup, SELECTOR_NAV_ITEMS)) {
          for (const item of SelectorEngine.children(navItem, SELECTOR_NAV_LINKS)) {
            item.classList.add(CLASS_NAME_ACTIVE)
          }
        }
      }
    }

    EventHandler.trigger(this._scrollElement, EVENT_ACTIVATE, {
      relatedTarget: target
    })
  }

  _clear() {
    const activeNodes = SelectorEngine.find(SELECTOR_LINK_ITEMS, this._config.target)
      .filter(node => node.classList.contains(CLASS_NAME_ACTIVE))

    for (const node of activeNodes) {
      node.classList.remove(CLASS_NAME_ACTIVE)
    }
  }

  // Static
  static jQueryInterface(config) {
    return this.each(function () {
      const data = ScrollSpy.getOrCreateInstance(this, config)

      if (typeof config !== 'string') {
        return
      }

      if (typeof data[config] === 'undefined') {
        throw new TypeError(`No method named "${config}"`)
      }

      data[config]()
    })
  }
}

/**
 * Data API implementation
 */

EventHandler.on(window, EVENT_LOAD_DATA_API, () => {
  for (const spy of SelectorEngine.find(SELECTOR_DATA_SPY)) {
    new ScrollSpy(spy) // eslint-disable-line no-new
  }
})

/**
 * jQuery
 */

defineJQueryPlugin(ScrollSpy)

export default ScrollSpy