npm install react-dropbox-chooser

<DropboxChooser 
    appKey={'your-uniq-app-key'}
    success={files => this.onSuccess(files)}
    cancel={() => this.onCancel()}
    multiselect={true}
    extensions={['.mp4']} >
    <div className="dropbox-button">Click me!</div>        
</DropboxChooser>

npm install
npm start
open http://localhost:8080