I think that he meant to say that V8 wasn't designed for long running processes like servers. In the browser it starts up, executes some code and then shuts down. Keep state around for a long time tends to lead to issues that take time to find / fix.
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There's no such thing as "client" or "server" languages.
Turing-complete languages like Javascript can be used for any purpose, regardless of its most common application.
Someone has even written a webserver in PostScript: http://www.pugo.org:8080/
Javascript is particularly well suited to evented style programming because it has a very simple support of first class functions.
I think that he meant to say that V8 wasn't designed for long running processes like servers. In the browser it starts up, executes some code and then shuts down. Keep state around for a long time tends to lead to issues that take time to find / fix.