Please send questions to the selenium user list [1]

[1] https://groups.google.com/forum/#!forum/selenium-users

I did. I've asked lots of people. No one knows. The bug is the lacking documentation
on the nodejs driver.

OK, the answer is: you can't
Use a proxy, e.g. https://github.com/webmetrics/browsermob-proxy

This is unfortunate. Maybe the documentation should be updated with a warning that the
official selnium node driver is incomplete?

Hey, is there a way to contribute to enable this? There definitely should be a way to
pass browser switches when starting the driver.

Hi all,

Is  there any way to change the user-agent using webdriverJs javascript on chrome browser
..

please give me information if any one know 

Thank you 
RAj

You can do it with Chrome, even though it's completely undocumented:

https://code.google.com/p/selenium/issues/detail?id=6189#makechanges

It's odd that the maintainers of this project don't know about it?

You do realize that your link doesn't go anywhere, right?

My bad, it was supposed to link to http://stackoverflow.com/questions/18501387/how-to-change-selenium-user-agent-in-selenium-webdriver-nodejs-land/23069825#23069825

Selenium does not provide API to change headers.

On the other hand, Selenium allows to pass arbitrary arguments to an executable driver
(for the browsers that has one -- IE, Chrome) or to an executable browser (PhantomJS).
So if a driver or a browser has an argument to change user-agent -- you're in luck.
But it is a workaround, not a Selenium feature.

Also you can use a proxy (e.g. browsermobproxy) as a man-in-the-middle to change headers.