bootstrap-vue/src/utils/bv-collapse.js

BootstrapVue, with over 40 plugins and more than 80 custom components, custom directives, and over 300 icons, provides one of the most comprehensive implementations of Bootstrap v4 components and grid system for Vue.js. With extensive and automated WAI-AR

// Generic collapse transion helper component
//
// Note:
//   Applies the classes `collapse`, `show` and `collapsing`
//   during the enter/leave transition phases only
//   Although it appears that Vue may be leaving the classes
//   in-place after the transition completes
import Vue from './vue'
import { mergeData } from 'vue-functional-data-merge'
import { getBCR, reflow, requestAF } from './dom'

// Transition event handler helpers
const onEnter = el => {
  el.style.height = 0
  // Animaton frame delay neeeded for `appear` to work
  requestAF(() => {
    reflow(el)
    el.style.height = `${el.scrollHeight}px`
  })
}

const onAfterEnter = el => {
  el.style.height = null
}

const onLeave = el => {
  el.style.height = 'auto'
  el.style.display = 'block'
  el.style.height = `${getBCR(el).height}px`
  reflow(el)
  el.style.height = 0
}

const onAfterLeave = el => {
  el.style.height = null
}

// Default transition props
// `appear` will use the enter classes
const TRANSITION_PROPS = {
  css: true,
  enterClass: '',
  enterActiveClass: 'collapsing',
  enterToClass: 'collapse show',
  leaveClass: 'collapse show',
  leaveActiveClass: 'collapsing',
  leaveToClass: 'collapse'
}

// Default transition handlers
// `appear` will use the enter handlers
const TRANSITION_HANDLERS = {
  enter: onEnter,
  afterEnter: onAfterEnter,
  leave: onLeave,
  afterLeave: onAfterLeave
}

// @vue/component
export const BVCollapse = /*#__PURE__*/ Vue.extend({
  name: 'BVCollapse',
  functional: true,
  props: {
    appear: {
      // If `true` (and `visible` is `true` on mount), animate initially visible
      type: Boolean,
      default: false
    }
  },
  render(h, { props, data, children }) {
    return h(
      'transition',
      // We merge in the `appear` prop last
      mergeData(data, { props: TRANSITION_PROPS, on: TRANSITION_HANDLERS }, { props }),
      // Note: `<tranition>` supports a single root element only
      children
    )
  }
})