<script type="application/javascript;version=1.7">
      // Old way of putting a series of numbers into an array
      var array = [];
      for ( var i = 0; i < 10; i++ ) {
          array.push( i );
      }
  
      // New way
      var array = [ i for ( i = 0; i < 10; i++ ) ];
  
      // Old way of putting object keys into an array
      var array = []
      for ( var key in obj ) {
           array.push( key );
      }
  
      // New Way
      var array = [ key for ( key in obj ) ];
  </script>