title: .map returning string in array instead of array of numbers
body: <p>Playing around with some code I found and the results do not make sense to me.  </p>
  
  <p>I do not understand why the REPL thinks the array is one long string value.. I have done nothing to indicate this is a string and I am wondering why the console is giving me the following result.</p>
  
  <pre><code>F = (...x) =&gt; x.map(v =&gt; x+1)
  
  //ACTUAL
  F([1,2,3]) //["1,2,31"]
  
  //EXPECTED
  F([1,2,3]) //[2,3,4]
  </code></pre>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var F =(...x) =&gt; x.map(v =&gt; x+1)  
  var result = F([1,2,3]);
  console.log(result);</code></pre>
  </div>
  </div>
  </p>