ant-design-vue/components/_util/openAnimation.js

import cssAnimation from './css-animation'
import getRequestAnimationFrame, { cancelRequestAnimationFrame } from './getRequestAnimationFrame'

const reqAnimFrame = getRequestAnimationFrame()

function animate (node, show, done) {
  let height
  let requestAnimationFrameId
  return cssAnimation(node, 'ant-motion-collapse', {
    start () {
      if (!show) {
        node.style.height = `${node.offsetHeight}px`
        node.style.opacity = 1
      } else {
        height = node.offsetHeight
        node.style.height = 0
        node.style.opacity = 0
      }
    },
    active () {
      if (requestAnimationFrameId) {
        cancelRequestAnimationFrame(requestAnimationFrameId)
      }
      requestAnimationFrameId = reqAnimFrame(() => {
        node.style.height = `${show ? height : 0}px`
        node.style.opacity = show ? 1 : 0
      })
    },
    end () {
      if (requestAnimationFrameId) {
        cancelRequestAnimationFrame(requestAnimationFrameId)
      }
      node.style.height = ''
      node.style.opacity = ''
      done()
    },
  })
}

const animation = {
  enter (node, done) {
    return animate(node, true, done)
  },
  leave (node, done) {
    return animate(node, false, done)
  },
}

export default animation