Sanitize string of regex characters before RegExp build?

I want to use a string to perform a global regex, but it might have regex characters in it. What's the best way to escape all regex characters in a string before building a regex with it? Basically I might have something like this; var test = 'test.'; var regex = new RegExp(test, 'ig'); I need 'test.' to become 'test\.' so it doesn't behave in unexpected ways.

[minodisk]

stringからRegExpインスタンスを作る際に特殊文字をエスケープする