What is the JavaScript equivalent of C# Server.URLEncode?

encodeURI()

http://xkr.us/articles/javascript/encode-compare/#ref-js-msdn

No, encodeURIComponent() exactly.

There’s a wonderful article on xkr.us comparing javascript’s various escape functions. Do read it for details, but here’s a quick summery:

• escape() — don’t use: does not understand non-ASCII characters, and does not escape some important URI characters, such as +.
• encodeURI() — encodes an entire URI: as such, it leaves ? and & unencoded.
• encodeURIComponent() — encodes a component in a query string (this is usually the one you want, and appears to be the equivalent of Server.URLEncode).