title: unique() for arrays in javascript
body: <p>As everybody knows there's no built-in function to remove the duplicates from an array in javascript. I've noticed this is also lacking in jQuery (which has a unique function for DOM selections only), and the most common snippet I found checks the entire array and a subset of it for each element (not very efficient I think), like:</p>
  
  <pre><code>for (var i = 0; i &lt; arr.length; i++)
      for (var j = i + 1; j &lt; arr.length; j++)
          if (arr[i] === arr[j])
              //whatever
  </code></pre>
  
  <p>so I made my own:</p>
  
  <pre><code>function unique (arr) {
      var hash = {}, result = [];
      for (var i = 0; i &lt; arr.length; i++)
          if (!(arr[i] in hash)) { //it works with objects! in FF, at least
              hash[arr[i]] = true;
              result.push(arr[i]);
          }
      return result;
  }
  </code></pre>
  
  <p>I wonder if there's any other algorithm accepted as the best for this case (or if you see any obvious flaw that could be fixed), or, what do you do when you need this in javascript (I'm aware that jQuery is not the only framework and some others may have this already covered).</p>