quasar/src/directives/Intersection.js

Build high-performance VueJS user interfaces (SPA, PWA, SSR, Mobile and Desktop) in record time

import { createDirective } from '../utils/private/create.js'
import { isDeepEqual } from '../utils/is.js'
import getSSRProps from '../utils/private/noop-ssr-directive-transform.js'

const defaultCfg = {
  threshold: 0,
  root: null,
  rootMargin: '0px'
}

function update (el, ctx, value) {
  let handler, cfg, changed

  if (typeof value === 'function') {
    handler = value
    cfg = defaultCfg
    changed = ctx.cfg === void 0
  }
  else {
    handler = value.handler
    cfg = Object.assign({}, defaultCfg, value.cfg)
    changed = ctx.cfg === void 0 || isDeepEqual(ctx.cfg, cfg) === false
  }

  if (ctx.handler !== handler) {
    ctx.handler = handler
  }

  if (changed === true) {
    ctx.cfg = cfg
    ctx.observer !== void 0 && ctx.observer.unobserve(el)

    ctx.observer = new IntersectionObserver(([ entry ]) => {
      if (typeof ctx.handler === 'function') {
        // if observed element is part of a vue transition
        // then we need to be careful...
        if (
          entry.rootBounds === null
          && document.body.contains(el) === true
        ) {
          ctx.observer.unobserve(el)
          ctx.observer.observe(el)
          return
        }

        const res = ctx.handler(entry, ctx.observer)

        if (
          res === false
          || (ctx.once === true && entry.isIntersecting === true)
        ) {
          destroy(el)
        }
      }
    }, cfg)

    ctx.observer.observe(el)
  }
}

function destroy (el) {
  const ctx = el.__qvisible

  if (ctx !== void 0) {
    ctx.observer !== void 0 && ctx.observer.unobserve(el)
    delete el.__qvisible
  }
}

export default createDirective(__QUASAR_SSR_SERVER__
  ? { name: 'intersection', getSSRProps }
  : {
      name: 'intersection',

      mounted (el, { modifiers, value }) {
        const ctx = {
          once: modifiers.once === true
        }

        update(el, ctx, value)

        el.__qvisible = ctx
      },

      updated (el, binding) {
        const ctx = el.__qvisible
        ctx !== void 0 && update(el, ctx, binding.value)
      },

      beforeUnmount: destroy
    }
)