This article briefly introduces the use of Html5's FormData to implement asynchronous uploading of files. It can also implement upload progress bars and file size verification. The code is simple and easy to understand, very good, and has reference value. Friends who need it can refer to it 1 Introduction Developing a file upload function is never a pleasant thing, especially asynchronous upload. I have used iframe and Flash upload solutions, and they all feel very awkward. This article briefly introduces the use of Html5's FormData to implement asynchronous uploading of files, and can also implement upload progress bars and file size verification. The server uses the springMVC solution for processing. 2 Html code