Masquerade/change HTTP_USER_AGENT string permanently using JavaScript?

Is there a way to cha开发者_高级运维nge/modify the value of user-agent string permanently using JavaScript?

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You mean from a web page inside a browser?

No, definitely not. Neither permanently nor temporarily.

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You can't even modify navigator.userAgent (at least on my test with Firefox).

So, no.

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Try this.

alert("User-agent header sent: " + navigator.userAgent);
navigator.__defineGetter__('userAgent', function(){ return "Hello" });
alert("User-agent header sent: " + navigator.userAgent);