HTML5's FILE api has a slice method that splits the BLOB object. The front end obtains the corresponding file through the FileList object, segments the large file according to the specified splitting manner, and then passes it to the back end one by one, and then the back end then splicing the files in a sequence.
At present, there are two commonly used methods for resuming breakpoints. One is to upload files through the websocket interface, and the other is through ajax. Both methods have their own advantages. Although websocket sounds more high-end, it uses different ones. The other algorithms outside the protocol are basically similar, and the server needs to open the ws interface. Here, the relatively convenient ajax is used to illustrate the idea of uploading the breakpoint.