ant-design-vue/components/vc-time-picker/Select.jsx

import PropTypes from '../_util/vue-types'
import BaseMixin from '../_util/BaseMixin'
import classnames from 'classnames'
function noop () {}
const scrollTo = (element, to, duration) => {
  const requestAnimationFrame = window.requestAnimationFrame ||
    function requestAnimationFrameTimeout () {
      return setTimeout(arguments[0], 10)
    }
  // jump to target if duration zero
  if (duration <= 0) {
    element.scrollTop = to
    return
  }
  const difference = to - element.scrollTop
  const perTick = difference / duration * 10

  requestAnimationFrame(() => {
    element.scrollTop = element.scrollTop + perTick
    if (element.scrollTop === to) return
    scrollTo(element, to, duration - 10)
  })
}

const Select = {
  mixins: [BaseMixin],
  props: {
    prefixCls: PropTypes.string,
    options: PropTypes.array,
    selectedIndex: PropTypes.number,
    type: PropTypes.string,
    // onSelect: PropTypes.func,
    // onMouseEnter: PropTypes.func,
  },
  data () {
    return {
      active: false,
    }
  },

  mounted () {
    this.$nextTick(() => {
      // jump to selected option
      this.scrollToSelected(0)
    })
  },
  watch: {
    selectedIndex (val) {
      this.$nextTick(() => {
        // smooth scroll to selected option
        this.scrollToSelected(120)
      })
    },
  },
  methods: {
    onSelect (value) {
      const { type } = this
      this.__emit('select', type, value)
    },

    getOptions () {
      const { options, selectedIndex, prefixCls } = this
      return options.map((item, index) => {
        const cls = classnames({
          [`${prefixCls}-select-option-selected`]: selectedIndex === index,
          [`${prefixCls}-select-option-disabled`]: item.disabled,
        })
        let onClick = noop
        if (!item.disabled) {
          onClick = this.onSelect.bind(this, item.value)
        }
        return (<li
          class={cls}
          key={index}
          onClick={onClick}
          disabled={item.disabled}
        >
          {item.value}
        </li>)
      })
    },

    scrollToSelected (duration) {
    // move to selected item
      const select = this.$el
      const list = this.$refs.list
      if (!list) {
        return
      }
      let index = this.selectedIndex
      if (index < 0) {
        index = 0
      }
      const topOption = list.children[index]
      const to = topOption.offsetTop
      scrollTo(select, to, duration)
    },

    handleMouseEnter (e) {
      this.setState({ active: true })
      this.__emit('mouseenter', e)
    },

    handleMouseLeave () {
      this.setState({ active: false })
    },
  },

  render () {
    if (this.options.length === 0) {
      return null
    }

    const { prefixCls } = this
    const cls = {
      [`${prefixCls}-select`]: 1,
      [`${prefixCls}-select-active`]: this.active,
    }

    return (
      <div
        class={cls}
        onMouseenter={this.handleMouseEnter}
        onMouseleave={this.handleMouseLeave}
      >
        <ul ref='list'>{this.getOptions()}</ul>
      </div>
    )
  },
}

export default Select