title: Very strange console.log behavior in Vuex actions
body: <p>The context: I'm developing a music app, which will have multiple "scenes", which each include collections of "tracks" (similiar to Ableton Live). When I add a new scene, somehow the new scene shows up with all the tracks which are on the first scene. This is reflected in the Vuex state (according to the DevTool), not just the rendering. (Also, if the tracks on the first scene are updated by the user, the tracks on the new scene change accordingly.) Instinctively, this feels like a pass-by-reference type of error, and I've been digging around trying to find it.</p>
  
  <p>What's really weirding me out though, is this:</p>
  
  <pre><code>actions: {
    setUpNewScene: context =&gt; {
      let newScene = JSON.parse(JSON.stringify(context.state.newSceneDefaults))
      console.log(context.state.newSceneDefaults)
      console.log(JSON.parse(JSON.stringify(context.state.newSceneDefaults)))
      console.log(newScene)
      // etc... 
  </code></pre>
  
  <p>Here is the beginning of the action which is called when the user clicks the "add new scene" button. The <em>first two</em> <code>console.logs</code> give exactly what you would expect: an object exactly resembling the <code>newSceneDefaults</code> as they are on the state (wherein <code>.tracks: [],</code>). The third <code>console.log</code> however, give that <em>plus the tracks from the first scene.</em></p>
  
  <p>This is exceptionally puzzling. It's as if somehow <code>newScene</code> is referencing a value from later on even though in the code it would appear to be executing sequentially. Is it possible that this is happening, somewhere in the inner workings of Vuex? Or else, what could be causing this behavior?</p>
  
  <p>I realize that it's hard to diagnose problems without seeing more of the code, which is why I'm focusing on the console.log right here. But of course, if you have encountered a situation like this and have any more general recommendations for solving it, I'm all ears. Thanks!</p>