<el-pagination 
    :current-page="currentPage" 
    @size-change="$utils.handleSizeChange(val)" 
    :page-sizes="[100, 20, 30, 40]" 
    layout="total, sizes, prev, pager, next, jumper" 
    :total=pageTotal>
</el-pagination>
export default {
handleSizeChange(val) {
    alert(val)
}} 
 this is the public method I wrote 
when I try to get val, prompt me for val undefind;
In the case ofelement-ui, the number of val currently displayed is obtained as follows:
  
 
< el-pagination
    :current-page="currentPage" 
    @size-change="handleSizeChange" 
    :page-sizes="[100, 20, 30, 40]" 
    layout="total, sizes, prev, pager, next, jumper" 
    :total=pageTotal>
</el-pagination>
methods: {
   handleSizeChange(val){
      console.log(val);
   }}
