title: Add numbers in Array using recursion and disregarding any other data type
body: <p>Forgive me if this is to basic or have been asked already, but I'm stuck at this problem and I feel like it must be something simple I'm not seeing.</p>
  
  <p>I want to add all numbers in the array using recursion(done!) and I'm missing a statement to ignore all other types of values. 
  For example: </p>
  
  <pre><code>var arr = [1,'a','b',2,[1],'c']
  sumValues(arr) // =&gt; 4 . 
  
  function sumValues(arr){
    if(arr.length === 0){
      return 0;
    } // if the array is empty
    if(arr.length &gt; 0){
      if(Array.isArray(arr[0])){
        return sumValues(arr[0]);
      } // if the next element is an array
      return arr.shift() + sumValues(arr);
    }
  }
  </code></pre>