<el-table v-loading="loading"
              :height="tableHeight"
              ref="tableRef"
              border
              stripe
              :data="marineSpecialList"
              @sort-change="sortChange">
      <el-table-column prop='shipmentDate' :sortable="true" width="45" align="center"/>
</el-table>




function sortChange(column){
  if((column.prop==='shipmentDate' || column.prop==='expectSailingStartDate') && column.order!==null){
    let arr = []
    marineSpecialList.value.map(item => {//遍历数组把有值放arr前面，空值放arr后面
      if(column.prop==='shipmentDate'){
        (item.shipmentDate === null) ? arr.push(item) : arr.unshift(item)
      }
      if(column.prop==='expectSailingStartDate'){
        (item.expectSailingStartDate === null) ? arr.push(item) : arr.unshift(item)
      }
    })
    marineSpecialList.value = arr
  }
}