title: How to move to prev/next element of an array
body: <p>Let's say we have a list of integers:</p>
  
  <pre><code>var fibonacci = [1,1,2,3,5,8,13,21];
  </code></pre>
  
  <p>I want to be able to get the next and previous element (just to move the element pointer, without modifying the array) in following manner (example, might go without prototype to redefine the Array interface but why not):</p>
  
  <pre><code>fibonacci.prev(); // returns false
  fibonacci.next(); // returns 1
  fibonacci.next(); // returns 1
  fibonacci.next(); // returns 2
  fibonacci.next(); // returns 3
  fibonacci.next(); // returns 5
  fibonacci.next(); // returns 8
  
  fibonacci.prev(); // returns 5
  
  fibonacci.next(); // returns 8
  fibonacci.next(); // returns 13
  fibonacci.next(); // returns false
  </code></pre>