title: How to reveal a React component on scroll
body: <p>I've created a React component for a fixed nav that I would like to remain hidden, until I scroll past a certain point on the page, then slides into view. <a href="https://medium.com/migration-issues/westeros-is-poorly-designed-3b01cf5cdcaf" rel="noreferrer">Medium</a> has a header similar to what I'm describing.</p>
  
  <p>This is a relatively trivial task in <a href="https://stackoverflow.com/questions/24765185/hide-fixed-header-on-scroll-down-show-on-scroll-up-and-hover">jQuery</a>, with scrollmagic or waypoints but is there an idiomatic way of accomplishing this with React and vanilla JS?</p>