computed: {
    tableRange() {
      const { tableHeaderData, tableDataList } = this
      return {
        tableHeaderData,
        tableDataList
      }
    }
  },
  watch: {
    tableRange(val) {
      const _this = this
      const tableDataList = val.tableDataList.slice(0, 10)
      const tableHeaderData = val.tableHeaderData
      if (tableDataList.length === 0) return
      var header = []
      tableHeaderData.forEach((item, index) => {
        header.push({ indexKey: index + 1 })
      })
      var obj = {}
      header.forEach(header => {
        obj[header.indexKey] = []
      })
      // 数据为空时，只获取表头的宽度自适应 // 数据不为空，全部数据宽度自适应
      tableHeaderData.forEach((head, headIndex) => {
        obj[headIndex + 1].push(head.description)
      })
      if (tableDataList.length > 0) {
        tableDataList.forEach((row, rowIndex) => {
          row.forEach((col, colIndex) => {
            for (var key in obj) {
              if (colIndex === Number(key)) {
                obj[key].push(col.text)
              }
            }
          })
        })
      }
      var totalWidth = 60
      tableHeaderData.forEach((value, index) => {
        const curWidth = _this.$getMaxLength(obj[index + 1])
        if (curWidth < 40) {
          value.width = 80
          totalWidth += 80
        } else if (curWidth >= 50 && curWidth < 80) {
          value.width = 130
          totalWidth += 130
        } else if (curWidth >= 80 && curWidth <= 100) {
          value.width = 150
          totalWidth += 150
        } else if (curWidth > 400) {
          value.width = 400
          totalWidth += 400
        } else {
          value.width = curWidth + 40
          totalWidth += curWidth + 40
        }
      })
      const TABLECONTENT = document.getElementById('TABLECONTENT')
      if (TABLECONTENT) {
        // 总宽度占不满整个table时，执行以下
        if (totalWidth < TABLECONTENT.offsetWidth) {
          _this.tableHeaderData.map(function(value) {
            value.width = 'auto'
          })
        }
      }
    }
  },

 html

<el-table-column
      v-for="(header,columnIndex) in tableHeaderData"
      :key="columnIndex"
      ref="sortColumn"
      :render-header="$labelHead"
      :prop="header[`orderByColumnName`]"
      :label="header.description"
      // 重点在这里
      :width="header.width"
      show-overflow-tooltip
      align="left">
      <template slot-scope="scope">
        ...
      </template>
    </el-table-column>

main.js  // 自适应table宽度，获取width

 $getMaxLength(arr) {
      if (arr) {
        return arr.reduce((acc, item) => {
          if (item) {
            const calcLen = this.$getTextWidth(item)
            if (acc < calcLen) {
              acc = calcLen
            }
          }
          return acc
        }, 0)
      } else {
        return 0
      }
    },
$getTextWidth(str) {
      let width = 0
      const html = document.createElement('span')
      html.innerText = str
      html.className = 'getTextWidth'
      document.querySelector('body').appendChild(html)
      width = document.querySelector('.getTextWidth').offsetWidth
      document.querySelector('.getTextWidth').remove()
      return width
    },