text: I have been following this tutorial on setting up React with Redux, and I noticed some syntax that I am not familiar with. What are the curly braces inside the function parameter definition doing?
  Example:
  function Stream({ tracks = [], onAuth }) { #what is going on here?
  return (
  <div>
  ... #component stuff here
  </div>
  );
  }
  It looks like destructuring syntax, but I didn't know javascript had destructuring.
  If that's what it is, the function is expecting an object with a
  tracks field (but can default to an empty list of the object doesn't Hebert one), and a
  onAuth field, which must be supplied. It's basically a neater way of accessing the passed object's fields.