const tableMixin = {
  data() {
    return {
      dragState: {}, // 记录子表的列宽移动的一些数值
      dragging: false // 子表是否在重置列宽
    }
  },
  methods: {
    handleMouseMove(event) {
      let target = event.target
      while (target && target.tagName !== 'TH') {
        target = target.parentNode
      }
      if (!this.dragging) {
        const rect = target.getBoundingClientRect()
        const bodyStyle = document.body.style
        if (rect.width > 12 && rect.right - event.pageX < 8) {
          // 拖拽的鼠标样式
          bodyStyle.cursor = 'col-resize'
        } else if (!this.dragging) {
          bodyStyle.cursor = ''
        }
      }
    },
    handleMouseOut() {
      document.body.style.cursor = ''
    },
    handleMouseDown(event) {
      // 开始拖拽
      this.dragging = true
      // 当前拖拽的列所在的表格
      let tableEl = event.target
      // 当前所在列（单元格）
      let thEL = event.target
      while (tableEl && tableEl.tagName !== 'TABLE') {
        tableEl = tableEl.parentNode
      }
      // 获取列宽拖拽的显示线（拖拽线）
      const resizeProxy = tableEl.querySelector('.table-column-line')
      while (thEL && thEL.tagName !== 'TH') {
        thEL = thEL.parentNode
      }
      const columnRect = thEL.getBoundingClientRect()
      thEL.classList.add('noclick')
      this.dragState = {
        startMouseLeft: event.clientX, // 鼠标开始的地方
        columnWidth: columnRect.width // th开始拖拽的宽度
      }
      resizeProxy.style.top = tableEl.getBoundingClientRect().top + 'px'
      // resizeProxy.style.height = tableEl.getBoundingClientRect().height + 'px'
      resizeProxy.style.left = this.dragState.startMouseLeft + 'px'
      resizeProxy.classList.remove('dn')
      document.onselectstart = function() {
        return false
      }
      document.ondragstart = function() {
        return false
      }
      const handleMouseMove = event => {
        // 拖拽中，拖拽线与鼠标的位置同步
        resizeProxy.style.left = event.clientX + 'px'
      }
      const handleMouseUp = () => {
        if (this.dragging) {
          // 拖拽完毕
          const { startMouseLeft, columnWidth } = this.dragState
          const finalLeft = parseInt(resizeProxy.style.left, 10)
          const columnWidthDiff = finalLeft - startMouseLeft
          const finalColumnWidth = columnWidthDiff + columnWidth
          const columnMinWidth = parseInt(thEL.style.minWidth, 10)
          thEL.style.width = finalColumnWidth + 'px'
          // 当单元格宽度改变时 表格宽度也进行改变: 1）有最小宽度时宽度改变了 2）无最小宽度时
          if (
            (columnMinWidth && finalColumnWidth >= columnMinWidth) ||
            !columnMinWidth
          ) {
            tableEl.style.width =
              columnWidthDiff + tableEl.clientWidth + 'px'
          }
          document.body.style.cursor = ''
          this.dragging = false
          this.dragState = {}
          resizeProxy.classList.add('dn')
        }

        document.removeEventListener('mousemove', handleMouseMove)
        document.removeEventListener('mouseup', handleMouseUp)
        document.onselectstart = null
        document.ondragstart = null
        setTimeout(function() {
          thEL.classList.remove('noclick')
        }, 0)
      }

      document.addEventListener('mousemove', handleMouseMove)
      document.addEventListener('mouseup', handleMouseUp)
    }
  }
}
export default tableMixin

【表格使用】

// 引入刚刚写的mixin
import tableMixin from './tableMixin'
// 引入混合
 mixins: [tableMixin]
// 在th表头写入
class="table-column-line"
 @mousemove="handleMouseMove"
 @mouseout="handleMouseOut"
 @mousedown="handleMouseDown"