Unit of Measure Conversion Library

Question

What is the best/most elegant way to abstract out the conversion of units of measures in the client, based on a user-preferred unit of measure setting?

For example,

Answer 1

Inspired by many posts regarding this subject and the simplicity and smallness of MomentJs i have started work on this:

MeasurementJs

It doesn't include all of the mentioned conversions yet, but you can easily extend the DEFINITIONS array and MeasurementJs.Units.* objects for any possible conversion you like.