前言

在我们项目开发中,经常会有布局拉伸的需求,接下来 让我们一步步用 vue指令 实现这个需求

先上 Demo 地址

codesandbox.io/s/dawn-cdn-…

常规使用

解决拉伸触发时机

既然我们使用了指令的方式,也就是牺牲了组件方式的绑定事件的便捷性.

那么我们如何来解决这个触发时机的问题呢?

在参考了 Element UI 的表格拉伸功能后,笔者受到了启发

有点抽象,这个红色区域可不是真实节点,只是笔者模拟的一个 boder-right 多说无益 直接上代码吧

const pointermove = e => {
    const { right } = el.getBoundingClientRect() // 获取到节点的右边界
    const { clientX } = e // 此时鼠标位置
    if (right - clientX < 8) // 表明在右边界的 8px 的过渡区 可以拉伸
}

实现一个简单的右拉伸

下面让我们来实现一个简单的右拉伸功能, 既然用指令 肯定是越简单越好

笔者决定用 vue提供的 修饰符, v-resize.right

实现 v-resize.right

1.首先我们创建两个相邻 div

<template>
  <div class="container">
    <div
      v-resize.right
      class="left"
    />
    <div class="right" />
  </div>
</template>
<style lang="scss" scoped>
.container {
  width: 400px;
  height: 100px;
  > div {
    float: left;
    height: 100%;
    width: 50%;
  }
  .left {
    background-color: lightcoral;
  }
  .right {
    background-color: lightblue;
  }
}
</style>

2.实现 resize 触发时机

export const resize = {
  inserted: function(el, binding) {
    el.addEventListener('pointermove', (e) => {
      const { right } = el.getBoundingClientRect()
      if (right - e.clientX < 8) {
        // 此时表明可以拉伸,时机成熟
        el.style.cursor = 'col-resize'
      } else {
        el.style.cursor = ''
      }
    })
  }
}

3.实现右拉伸功能

el.addEventListener('pointerdown', (e) => {
  const rightDom = el.nextElementSibling // 获取右节点
  const startX = e.clientX // 获取当前点击坐标

  const { width } = el.getBoundingClientRect() // 获取当前节点宽度
  const { width: nextWidth } = rightDom.getBoundingClientRect() // 获取右节点宽度
  el.setPointerCapture(e.pointerId) // HTML5 的 API 自行百度~

  const onDocumentMouseMove = (e) => {
    const offsetX = e.clientX - startX // 此时的 x 坐标偏差
    // 更新左右节点宽度
    el.style.width = width + offsetX + 'px'
    rightDom.style.width = nextWidth - offsetX + 'px'
  }
  // 因为此时我们要在整个屏幕移动 所以我们要在 document 挂上 mousemove
  document.addEventListener('mousemove',onDocumentMouseMove)

让我们看看此时的效果

会发现有两个问题

1. 左边宽度会>左右之和,右边宽度会 < 0
2. 当我们鼠标弹起的时候 还能继续拉伸

让我们首先解决第一个问题

方案一:限制最小宽度

const MIN_WIDTH = 10
document.addEventListener('mousemove', (e) => {
    const offsetX = e.clientX - startX // 此时的 x 坐标偏差
    +if (width + offsetX < MIN_WIDTH || nextWidth - offsetX < MIN_WIDTH) return
    // 更新左右节点宽度
    el.style.width = width + offsetX + 'px'
    rightDom.style.width = nextWidth - offsetX + 'px'
})

第二个问题,其实非常简单

方案二:鼠标弹起后释放对应拉伸事件

el.addEventListener('pointerup', (e) => {
    el.releasePointerCapture(e.pointerId)
    document.removeEventListener('mousemove', onDocumentMouseMove)
})

此时最最最基础的 v-resize 左右拉伸版本 我们已经实现了,来看下效果吧

看下此时的完整代码

export const resize = {
  inserted: function (el, binding) {
    el.addEventListener('pointermove', (e) => {
      const { right } = el.getBoundingClientRect()
      if (right - e.clientX < 8) {
        // 此时表明可以拉伸
        el.style.cursor = 'col-resize'
      } else {
        el.style.cursor = ''
      }
    })

    const MIN_WIDTH = 10

    el.addEventListener('pointerdown', (e) => {
      const rightDom = el.nextElementSibling // 获取右节点
      const startX = e.clientX // 获取当前点击坐标

      const { width } = el.getBoundingClientRect() // 获取当前节点宽度
      const { width: nextWidth } = rightDom.getBoundingClientRect() // 获取右节点宽度
      el.setPointerCapture(e.pointerId) // HTML5 的 API 自行百度~

      const onDocumentMouseMove = (e) => {
        const offsetX = e.clientX - startX // 此时的 x 坐标偏差
        if (width + offsetX < MIN_WIDTH || nextWidth - offsetX < MIN_WIDTH) {
          return
        }
        // 更新左右节点宽度
        el.style.width = width + offsetX + 'px'
        rightDom.style.width = nextWidth - offsetX + 'px'
      }
      // 因为此时我们要在整个屏幕移动 所以我们要在 document 挂上 mousemove
      document.addEventListener('mousemove', onDocumentMouseMove)

      el.addEventListener('pointerup', (e) => {
        el.releasePointerCapture(e.pointerId)
        document.removeEventListener('mousemove', onDocumentMouseMove)
      })
    })
  },
}

作为 一名 优秀的前端性能优化专家, 我想你此刻已经要吐槽了,这么多 EventListener 都不移除吗? 是的,后续代码我们将会移除这些被绑定的事件(此处非重点 不做赘叙)

实现完 右拉伸 想必你对 左,上,下拉伸 也已经有了自己的思路

开始进阶

接下来让我们看下这种场景

我们 想实现一个 两边能同时拉伸的功能, 也就是 v-resize.left.right

实现左右拉伸功能

这种场景比较复杂,就需要我们维护一个拉伸方向上的变量 position

实现 v-resize.left.right

export const resize = {
  inserted: function (el, binding) {
    let position = '',
      resizing = false
    el.addEventListener('pointermove', (e) => {
      if (resizing) return
      const { left, right } = el.getBoundingClientRect()
      const { clientX } = e
      if (right - clientX < 8) {
        position = 'right' // 此时表明右拉伸
        el.style.cursor = 'col-resize'
      } else if (clientX - left < 8) {
        position = 'left' // 此时表明左拉伸
        el.style.cursor = 'col-resize'
      } else {
        position = ''
        el.style.cursor = ''
      }
    })

    const MIN_WIDTH = 10

    el.addEventListener('pointerdown', (e) => {
      if (position === '') return
      const sibling = position === 'right' ? el.nextElementSibling : el.previousElementSibling // 获取相邻节点
      const startX = e.clientX // 获取当前点击坐标

      const { width } = el.getBoundingClientRect() // 获取当前节点宽度
      const { width: siblingWidth } = sibling.getBoundingClientRect() // 获取右节点宽度
      el.setPointerCapture(e.pointerId) // HTML5 的 API 自行百度~

      const onDocumentMouseMove = (e) => {
        resizing = true
        if (position === '') return
        const offsetX = e.clientX - startX
        const _elWidth = position === 'right' ? width + offsetX : width - offsetX //判断左右拉伸 所影响的当前节点宽度

        const _siblingWidth = position === 'right' ? siblingWidth - offsetX : siblingWidth + offsetX //判断左右拉伸 所影响的相邻节点宽度
        if (_elWidth <= MIN_WIDTH || _siblingWidth <= MIN_WIDTH) return

        // 更新左右节点宽度
        el.style.width = _elWidth + 'px'
        sibling.style.width = _siblingWidth + 'px'
      }

      document.addEventListener('mousemove', onDocumentMouseMove)

      el.addEventListener('pointerup', (e) => {
        position = ''
        resizing = false
        el.releasePointerCapture(e.pointerId)
        document.removeEventListener('mousemove', onDocumentMouseMove)
      })
    })
  },
}

看下此时的效果

非常丝滑, 当然 我们还需要考虑 传递 最小宽度 最大宽度 过渡区 等多种业务属性,但是这对于各位看官来说都是鸡毛蒜皮的小事. 自行改造就行了

完整代码

const MIN_WIDTH = 50
const MIN_HEIGHT = 50
const elEventsWeakMap = new WeakMap()

function getElStyleAttr(element, attr) {
  const styles = window.getComputedStyle(element)
  return styles[attr]
}

function getSiblingByPosition(el, position) {
  const siblingMap = {
    left: el.previousElementSibling,
    right: el.nextElementSibling,
    bottom: el.nextElementSibling,
    top: el.previousElementSibling
  }
  return siblingMap[position]
}

const initResize = ({
  el,
  positions,
  minWidth = MIN_WIDTH,
  minHeight = MIN_HEIGHT
}) => {
  if (!el) return
  const resizeState = {}
  const defaultCursor = getElStyleAttr(el, 'cursor')
  const elStyle = el.style

  const canLeftResize = positions.includes('left')
  const canRightResize = positions.includes('right')
  const canTopResize = positions.includes('top')
  const canBottomResize = positions.includes('bottom')

  if (!canLeftResize && !canRightResize && !canTopResize && !canBottomResize) {
    return
  } // 未指定方向

  const pointermove = (e) => {
    if (resizeState.resizing) return
    const { left, right, top, bottom } = el.getBoundingClientRect()
    const { clientX, clientY } = e
    // 左右拉伸
    if (canLeftResize || canRightResize) {
      if (clientX - left < 8) resizeState.position = 'left'
      else if (right - clientX < 8) resizeState.position = 'right'
      else resizeState.position = ''

      if (resizeState.position === '') {
        elStyle.cursor = defaultCursor
      } else {
        elStyle.cursor = 'col-resize'
        e.stopPropagation()
      }
    } else if (canTopResize || canBottomResize) {
      // 上下拉伸
      if (clientY - top < 8) resizeState.position = 'top'
      else if (bottom - clientY < 8) resizeState.position = 'bottom'
      else resizeState.position = ''

      if (resizeState.position === '') {
        elStyle.cursor = defaultCursor
      } else {
        elStyle.cursor = 'row-resize'
        e.stopPropagation()
      }
    }
  }

  const resizeEnd = (e) => {
    e.stopPropagation()
    resizeState.position = ''
    resizeState.resizing = false
    elStyle.cursor = defaultCursor
    el.releasePointerCapture(e.pointerId)
    document.removeEventListener('mousemove', resizeState.onDocumentMouseMove)
    resizeState.onDocumentMouseMove = null
  }
  // todo 只有在命中mousemove可拖拽的情况下 添加事件
  const pointerdown = (e) => {
    const { resizing, position } = resizeState
    if (resizing || !position) return

    if (position) e.stopPropagation() // 如果当前节点存在拉伸方向 需要组织冒泡
    el.setPointerCapture(e.pointerId)

    const isFlex = getElStyleAttr(el.parentNode, 'display') === 'flex'

    resizeState.resizing = true
    resizeState.startMouseX = e.clientX
    resizeState.startMouseY = e.clientY

    const { width, height } = el.getBoundingClientRect()

    const containerSibling = getSiblingByPosition(el, position)
    if (!containerSibling) {
      console.error('未找到兄弟节点', position)
      return
    }

    const rectSibling = containerSibling.getBoundingClientRect()

    const { startMouseX, startMouseY } = resizeState
    const onDocumentMouseMove = (e) => {
      if (!resizeState.resizing) return
      elStyle.cursor =
        canLeftResize || canRightResize ? 'col-resize' : 'col-row'
      const { clientX, clientY } = e

      if (position === 'left' || position === 'right') {
        const offsetX = clientX - startMouseX
        const elWidth = position === 'right' ? width + offsetX : width - offsetX

        const containerSiblingWidth =
          position === 'right'
            ? rectSibling.width - offsetX
            : rectSibling.width + offsetX
        if (elWidth <= minWidth || containerSiblingWidth <= minWidth) return

        el.style.width = elWidth + 'px'
        containerSibling.style.width = containerSiblingWidth + 'px'
        if (isFlex) {
          el.style['min-width'] = elWidth + 'px'
          containerSibling.style['min-width'] = containerSiblingWidth + 'px'
        }
      } else if (position === 'top' || position === 'bottom') {
        const offsetY = clientY - startMouseY
        const elHeight =
          position === 'bottom' ? height + offsetY : height - offsetY

        const containerSiblingHeight =
          position === 'bottom'
            ? rectSibling.height - offsetY
            : rectSibling.height + offsetY
        if (elHeight <= minHeight || containerSiblingHeight <= minHeight) return

        el.style.height = elHeight + 'px'
        containerSibling.style.height = containerSiblingHeight + 'px'
        if (isFlex) {
          el.style['min-height'] = elHeight + 'px'
          containerSibling.style['min-height'] = containerSiblingHeight + 'px'
        }
      }
    }
    resizeState.onDocumentMouseMove = onDocumentMouseMove
    document.addEventListener('mousemove', onDocumentMouseMove)
  }

  const bindElEvents = () => {
    el.addEventListener('pointermove', pointermove)
    el.addEventListener('pointerleave', resizeEnd)
    el.addEventListener('pointerup', resizeEnd)
    el.addEventListener('pointerdown', pointerdown)
  }

  const unBindElEvents = () => {
    el.removeEventListener('pointermove', pointermove)
    el.removeEventListener('pointerleave', resizeEnd)
    el.removeEventListener('pointerup', resizeEnd)
    el.removeEventListener('pointerdown', pointerdown)
  }

  bindElEvents()

  // 设置解绑事件
  elEventsWeakMap.set(el, unBindElEvents)
}
export const resize = {
  inserted: function(el, binding) {
    const { modifiers, value: { minWidth, minHeight } = {}} = binding
    const positions = Object.keys(modifiers)
    initResize({ el, positions, minWidth, minHeight })
  },
  unbind: function(el) {
    const unBindElEvents = elEventsWeakMap.get(el)
    unBindElEvents()
  }
}

参考文章

juejin.cn/post/698238… juejin.cn/post/724593…

写在最后

未来想做的还有很多

• 支持 % 比的配置
• 支持 嵌套类型的 父子孙节点的更新
• ...

个人能力有限 如有不对,欢迎指正🌟 如有帮助,建议小心心大拇指三连🌟