Why does the browser replace + in a request with a space?

Question

JavaScript

I send in the request (post and get behave the same)

PGEgY2xhc3M9Im5ld3NfdGl0bGVzIiBocmVmPSIiPtC+PC9hPg==

reaches the server

PGEgY2xhc3M9Im5ld3NfdGl0bGVzIiBocmVmPSIiPtC PC9hPg==

so I solved the problem by replacing + with %2B
but the reason is not clear because encodeURI + ignores

Answer 1

encodeURI ignores + because it is a valid URI character used to pass a space.
Use encodeURIComponent .