The front-end downloads files, and the back-end sends gzip files. Is there a way to get the file size?

Download files from the front end , From the back end is gzip Type of , Is there any way to get this file size ？
Because you need to download the progress bar .

If the server does not return content-length You can't make a download progress bar with progress tips , Whether or not gzip resources , Because you can't know in advance how big the resources are .

Refer to the browser when downloading, there is no centent-length Only download speed and current download size are available for resource download , No percentage display .

Not all resources can be returned to you conent-length Of , For streaming data, there is basically no such header , You have to consider this scenario

Refer to this article ：《 How to implement a download progress bar / Play progress bar 》