The answer would depend on your use case.

1. Are you trying to get an existing code base to run pretty much as is in the context of a browser or some JavaScript environment? If so, you might want to look intoopal instead.
2. Are you trying to migrate your code from Ruby to JavaScript? If so, be aware that JavaScript doesn't have exact equivalents to everything that Ruby has, so at best the conversion will be 80 to 95% successful. The statement above likely would map to animport statement, or perhaps a CJS require, but will require some manual editing to complete. Additionally, JavaScript has no native equivalent toFile.expand_path, the closest it has ispath.resolve which is roughly equivalent to Ruby'sFile.absolute_path.
3. Are you trying to make use of an platform API that typically is only made available in JavaScript but you want to leverage your existing skills in Ruby? This use case differs significantly from the previous two in that you generally aren't starting with an existing code base.