title: ES6 Array destructuring weirdness
body: <p>Can anyone explain, why the following happens with ES6 array destructuring?</p>
  
  <pre><code>let a, b, c
  [a, b] = ['A', 'B']
  [b, c] = ['BB', 'C']
  console.log(`a=${a} b=${b} c=${c}`)
  
  // expected: a=A b=BB c=C
  // actual:   a=BB b=C c=undefined
  </code></pre>
  
  <p><a href="http://codepen.io/ronkot/pen/WxRqXg?editors=0011" rel="noreferrer">http://codepen.io/ronkot/pen/WxRqXg?editors=0011</a></p>