ant-design/components/upload/demo/beforeUpload.md

order	title
7	[{zh-CN 限制用户上传的文件} {en-US Filter uploads files}]

zh-CN

可以通过 beforeUpload 在文件上传之前进行干预，如限制用户只能上传 JPG 文件。

也支持异步检查，beforeUpload 的返回值可以是一个 Promise：示例。

en-US

You can use beforeUpload to check whether user can upload, for example, limit file type only to be JPG. Checking can also be asynchronous. The return value can also be a Promise for function beforeUpload

import { Upload, Button, Icon, message } from 'antd';

const props = {
  action: '/upload.do',
  beforeUpload(file) {
    const isJPG = file.type === 'image/jpeg';
    if (!isJPG) {
      message.error('you can only upload JPG file~');
    }
    return isJPG;
  },
};

ReactDOM.render(
  <Upload {...props}>
    <Button type="ghost">
      <Icon type="upload" /> upload
    </Button>
  </Upload>
, mountNode);