lib/js/src/scrollspy.js

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

import {
    defineJQueryPlugin,
    getElement,
    getSelectorFromElement,
    typeCheckConfig
} 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 Default = {
    offset: 10,
    method: 'auto',
    target: ''
}

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

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'

/**
 * ------------------------------------------------------------------------
 * Class Definition
 * ------------------------------------------------------------------------
 */

class ScrollSpy extends BaseComponent {
    constructor(element, config) {
        super(element)
        this._scrollElement = this._element.tagName === 'BODY' ? window : this._element
        this._config = this._getConfig(config)
        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 NAME() {
        return NAME
    }

    // Public

    refresh() {
        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

        this._offsets = []
        this._targets = []
        this._scrollHeight = this._getScrollHeight()

        const targets = SelectorEngine.find(SELECTOR_LINK_ITEMS, this._config.target)

        targets.map(element => {
                const targetSelector = getSelectorFromElement(element)
                const target = targetSelector ? SelectorEngine.findOne(targetSelector) : null

                if (target) {
                    const targetBCR = target.getBoundingClientRect()
                    if (targetBCR.width || targetBCR.height) {
                        return [
                            Manipulator[offsetMethod](target).top + offsetBase,
                            targetSelector
                        ]
                    }
                }

                return null
            })
            .filter(item => item)
            .sort((a, b) => a[0] - b[0])
            .forEach(item => {
                this._offsets.push(item[0])
                this._targets.push(item[1])
            })
    }

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

    // Private

    _getConfig(config) {
        config = {
            ...Default,
            ...Manipulator.getDataAttributes(this._element),
            ...(typeof config === 'object' && config ? config : {})
        }

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

        typeCheckConfig(NAME, config, DefaultType)

        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 (let i = this._offsets.length; i--;) {
            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 {
            SelectorEngine.parents(link, SELECTOR_NAV_LIST_GROUP)
                .forEach(listGroup => {
                    // Set triggered links parents as active
                    // With both <ul> and <nav> markup a parent is the previous sibling of any nav ancestor
                    SelectorEngine.prev(listGroup, `${SELECTOR_NAV_LINKS}, ${SELECTOR_LIST_ITEMS}`)
                        .forEach(item => item.classList.add(CLASS_NAME_ACTIVE))

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

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

    _clear() {
        SelectorEngine.find(SELECTOR_LINK_ITEMS, this._config.target)
            .filter(node => node.classList.contains(CLASS_NAME_ACTIVE))
            .forEach(node => 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, () => {
    SelectorEngine.find(SELECTOR_DATA_SPY)
        .forEach(spy => new ScrollSpy(spy))
})

/**
 * ------------------------------------------------------------------------
 * jQuery
 * ------------------------------------------------------------------------
 * add .ScrollSpy to jQuery only if jQuery is present
 */

defineJQueryPlugin(ScrollSpy)

export default ScrollSpy