title: How to replace therubyracer javascript runtime
body: <p>How do I replace the <code>therubyracer</code> gem?  I'm really stuck.</p>
  <p>We have been using the <code>therubyracer</code> gem for our Rails asset pipeline.  However, it is using dependencies which are past their end of life and have security vulnerabilities.  The latest version <code>0.12.3</code> is from January 05, 2017.</p>
  <p>I have looked at the <code>mini_racer</code> gem, but we deploy to FreeBSD and the latest version supported on FreeBSD is <code>0.1.14</code> from August 24, 2017.  We develop on macOS and my compile of this version of <code>mini_racer</code> gets errors, one of which because <code>CreateDefaultPlatform</code> has been removed from V8.</p>
  <p>The list of runtimes supported by execjs, at <a href="https://github.com/rails/execjs" rel="nofollow noreferrer">https://github.com/rails/execjs</a> lists <code>Node.js</code> and <code>Google V8</code> but the links go to pages which don't look like gems I can replace in my Gemfile, neither do those pages have documentation on how to use their runtime for execjs.  I honestly am stuck with no idea how to use a newer runtime in my Rails pipeline.</p>