reactjs - Programmatically navigate using react router

With react-router I can use the Link element to create links that are natively handled by react router.

I see internally it calls this.context.transitionTo(...).

I want to do a navigation, but not from a link, from a dropdown selection for example. How can I do this in code? What is this.context?

I saw the Navigation mixin, but can I do this without mixins?