upload excel file on client side

Do you mean you want to upload a file from server to client without viewing it, and save the file locally? If yes, you can find useful information here:
https://stackoverflow.com/questions/24401680/file-uploading-in-a-local-drive-with-angularjs
But if you are looking for general upload samples, you can find more details in the following thread:
https://stackoverflow.com/questions/13963022/angularjs-how-to-implement-a-simple-file-upload-with-multipart-form

However, if you mean you want the client to upload the Excel files and view them, and then resave them locally as Excel or any other document format; you can do this using the HTML5/JavaScript Document Viewer control from LEADTOOLS.
You can check an online demo here:
https://demo.leadtools.com/JavaScript/DocumentViewer/
After this, you can check the following thread (with sample code) about using the document viewer with Angular2 application:
https://www.leadtools.com/support/forum/posts/t12485-How-To--Use-the-Document-Viewer-in-an-Angular2-Application