main.ts:20 ElementPlusError: [ElPagination] Deprecated usages detected, please refer to the el-pagination documentation for more details
    at debugWarn (error.ts:13:37)
    at Proxy.<anonymous> (pagination.ts:203:9)
    at renderComponentRoot (runtime-core.esm-bundler.js:914:44)
    at ReactiveEffect.componentUpdateFn [as fn] (runtime-core.esm-bundler.js:5649:57)
    at ReactiveEffect.run (reactivity.esm-bundler.js:190:25)
    at instance.update (runtime-core.esm-bundler.js:5763:56)
    at setupRenderEffect (runtime-core.esm-bundler.js:5777:9)
    at mountComponent (runtime-core.esm-bundler.js:5559:9)
    at processComponent (runtime-core.esm-bundler.js:5517:17)
    at patch (runtime-core.esm-bundler.js:5119:21)

引起以上警告信息的代码如下：

<el-pagination 
    :current-page="p.page + 1" 
    :page-size="p.pageSize" 
    :page-sizes="[10, 15, 20, 50]"
    background 
    layout="total, sizes, prev, pager, next, jumper"
    :total="tableData.totalElements"                   这一行引发错误
    @update:page-size="handleSizeChange" 
    @update:current-page="handleCurrentChange"/>

引起错误的原因是  :total属性赋值必须为数字类型。修改为如下即可：

:total="parseInt(tableData.totalElements)"